{"slug":"addyosmani-api-and-interface-design","name":"api-and-interface-design","description":"Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.","long_description":"---\nname: api-and-interface-design\ndescription: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.\n---\n\n# API and Interface Design\n\n## Overview\n\nDesign stable, well-documented interfaces that are hard to misuse. Good interfaces make the right thing easy and the wrong thing hard. This applies to REST APIs, GraphQL schemas, module boundaries, component props, and any surface where one piece of code talks to another.\n\n## When to Use\n\n- Designing new API endpoints\n- Defining module boundaries or contracts between teams\n- Creating component prop interfaces\n- Establishing database schema that informs API shape\n- Changing existing public interfaces\n\n## Core Principles\n\n### Hyrum's Law\n\n> With a sufficient number of users of an API, all observable behaviors of your system will be depended on by somebody, regardless of what you promise in the contract.\n\nThis means: every public behavior — including undocumented quirks, error message text, timing, and ordering — becomes a de facto contract once users depend on it. Design implications:\n\n- **Be intentional about what you expose.** Every observable behavior is a potential commitment.\n- **Don't leak implementation details.** If users can observe it, they will depend on it.\n- **Plan for deprecation at design time.** See `deprecation-and-migration` for how to safely remove things users depend on.\n- **Tests are not enough.** Even with perfect contract tests, Hyrum's Law means \"safe\" changes can break real users who depend on undocumented behavior.\n\n### The One-Version Rule\n\nAvoid forcing consumers to choose between multiple versions of the same dependency or API. Diamond dependency problems arise when different consumers need different versions of the same thing. Design for a world where only one version exists at a time — extend rather than fork.\n\n### 1. Contract First\n\nDefine the interface before implementing it. The contract is the spec — implementation follows.\n\n```typescript\n// Define the contract first\ninterface TaskAPI {\n  // Creates a task and returns the created task with server-generated fields\n  createTask(input: CreateTaskInput): Promise<Task>;\n\n  // Returns paginated tasks matching filters\n  listTasks(params: ListTasksParams): Promise<PaginatedResult<Task>>;\n\n  // Returns a single task or throws NotFoundError\n  getTask(id: string): Promise<Task>;\n\n  // Partial update — only provided fields change\n  updateTask(id: string, input: UpdateTaskInput): Promise<Task>;\n\n  // Idempotent delete — succeeds even if already deleted\n  deleteTask(id: string): Promise<void>;\n}\n```\n\n### 2. Consistent Error Semantics\n\nPick one error strategy and use it everywhere:\n\n```typescript\n// REST: HTTP status codes + structured error body\n// Every error response follows the same shape\ninterface APIError {\n  error: {\n    code: string;        // Machine-readable: \"VALIDATION_ERROR\"\n    message: string;     // Human-readable: \"Email is required\"\n    details?: unknown;   // Additional context when helpful\n  };\n}\n\n// Status code mapping\n// 400 → Client sent invalid data\n// 401 → Not authenticated\n// 403 → Authenticated but not authorized\n// 404 → Resource not found\n// 409 → Conflict (duplicate, version mismatch)\n// 422 → Validation failed (semantically invalid)\n// 500 → Server error (never expose internal details)\n```\n\n**Don't mix patterns.** If some endpoints throw, others return null, and others return `{ error }` — the consumer can't predict behavior.\n\n### 3. Validate at Boundaries\n\nTrust internal code. Validate at system edges where external input enters:\n\n```typescript\n// Validate at the API boundary\napp.post('/api/tasks', async (req, res) => {\n  const result = CreateTaskSchema.safeParse(req.body);\n  if (!result.success) {\n    return res.status(422).json({\n      error: {\n        code: 'VALIDATION_ERROR',\n        message: 'Invalid task data',\n        details: result.error.flatten(),\n      },\n    });\n  }\n\n  // After validation, internal code trusts the types\n  const task = await taskService.create(result.data);\n  return res.status(201).json(task);\n});\n```\n\nWhere validation belongs:\n- API route handlers (user input)\n- Form submission handlers (user input)\n- External service response parsing (third-party data -- **always treat as untrusted**)\n- Environment variable loading (configuration)\n\n> **Third-party API responses are untrusted data.** Validate their shape and content before using them in any logic, rendering, or decision-making. A compromised or misbehaving external service can return unexpected types, malicious content, or instruction-like text.\n\nWhere validation does NOT belong:\n- Between internal functions that share type contracts\n- In utility functions called by already-validated code\n- On data that just came from your own database\n\n### 4. Prefer Addition Over Modification\n\nExtend interfaces without breaking existing consumers:\n\n```typescript\n// Good: Add optional fields\ninterface CreateTaskInput {\n  title: string;\n  description?: string;\n  priority?: 'low' | 'medium' | 'high';  // Added later, optional\n  labels?: string[];                       // Added later, optional\n}\n\n// Bad: Change existing field types or remove fields\ninterface CreateTaskInput {\n  title: string;\n  // description: string;  // Removed — breaks existing consumers\n  priority: number;         // Changed from string — breaks existing consumers\n}\n```\n\n### 5. Predictable Naming\n\n| Pattern | Convention | Example |\n|---------|-----------|---------|\n| REST endpoints | Plural nouns, no verbs | `GET /api/tasks`, `POST /api/tasks` |\n| Query params | camelCase | `?sortBy=createdAt&pageSize=20` |\n| Response fields | camelCase | `{ createdAt, updatedAt, taskId }` |\n| Boolean fields | is/has/can prefix | `isComplete`, `hasAttachments` |\n| Enum values | UPPER_SNAKE | `\"IN_PROGRESS\"`, `\"COMPLETED\"` |\n\n### 6. Honouring an Idempotency Key\n\nAccepting an `Idempotency-Key` is the contract. Honouring it is the implementation, and it is where the money is lost — a key the server accepts but handles carelessly is worse than no key at all, because the client now believes retrying is safe.\n\n**Derive the key from the intent, not the attempt.** The key must be stable across retries of one intent and different across distinct intents:\n\n```typescript\ncrypto.randomUUID()                    // ✗ new key per attempt — every retry is a new charge\n`${userId}:${amount}`                  // ✗ two legitimate $50 charges collapse into one\n`${orderId}:${Date.now()}`             // ✗ a timestamp is randomUUID() wearing a hat\n\nreq.headers['idempotency-key']         // ✓ client generates once, reuses on retry\n`charge:v1:${orderId}`                 // ✓ derived from an immutable identifier\n```\n\nThe key comes from the client or the initiating event — never from the layer doing the retrying.\n\n**Claim atomically. A check followed by an act is a race:**\n\n```typescript\n// ✗ TOCTOU: two concurrent retries both read \"not seen\", both charge\nif (!(await db.exists(key))) {\n  await chargeCard(amount);\n  await db.insert(key);\n}\n\n// ✓ let the unique constraint pick the winner\ntry {\n  await db.insert({ key, state: 'in_progress', requestHash });\n} catch (e) {\n  if (isUniqueViolation(e)) return replayOrReject(key);\n  throw;\n}\nconst result = await chargeCard(amount);\nawait db.update({ key, state: 'succeeded', response: result });\n```\n\nThe unique constraint *is* the mechanism. A store that cannot enforce uniqueness in one operation cannot back this.\n\n**Guard the payload.** Same key with a different body is a client bug, and must fail loudly rather than serving the first response to a second request:\n\n```typescript\nif (existing.requestHash !== hash(req.body)) {\n  return res.status(422).json({ error: 'idempotency key reused with a different payload' });\n}\n```\n\n**Decide what an in-flight duplicate gets.** The first request is still running when the second arrives — the common case under retry storms:\n\n| Strategy | Response | Use when |\n|---|---|---|\n| Reject | `409 Conflict` | Client can retry later; simplest and safest |\n| Wait | Block for the result, bounded | Caller needs it synchronously |\n| Return pending | `202` + status URL | Long-running effects |\n\nNever let the second caller through because the first \"seems stuck\". A stalled attempt whose fate is unknown is exactly when duplicating costs most.\n\n**Every call has three outcomes, not two: success, failure, and _unknown_.** A timeout tells you nothing about whether the effect applied. Record the intent *before* calling out, so a crash between the call and the response leaves evidence something must resolve later — rather than a silently retried charge.\n\n**Set retention from the longest retry chain**, not from disk cost. Keys must outlive every path that can re-deliver the same intent, including a dead-letter queue replayed a week later and any provider dispute window. A 24-hour key TTL behind a 7-day DLQ is a duplicate waiting to happen.\n\n## REST API Patterns\n\n### Resource Design\n\n```\nGET    /api/tasks              → List tasks (with query params for filtering)\nPOST   /api/tasks              → Create a task\nGET    /api/tasks/:id          → Get a single task\nPATCH  /api/tasks/:id          → Update a task (partial)\nDELETE /api/tasks/:id          → Delete a task\n\nGET    /api/tasks/:id/comments → List comments for a task (sub-resource)\nPOST   /api/tasks/:id/comments → Add a comment to a task\n```\n\n### Pagination\n\nPaginate list endpoints:\n\n```typescript\n// Request\nGET /api/tasks?page=1&pageSize=20&sortBy=createdAt&sortOrder=desc\n\n// Response\n{\n  \"data\": [...],\n  \"pagination\": {\n    \"page\": 1,\n    \"pageSize\": 20,\n    \"totalItems\": 142,\n    \"totalPages\": 8\n  }\n}\n```\n\n### Filtering\n\nUse query parameters for filters:\n\n```\nGET /api/tasks?status=in_progress&assignee=user123&createdAfter=2025-01-01\n```\n\n### Partial Updates (PATCH)\n\nAccept partial objects — only update what's provided:\n\n```typescript\n// Only title changes, everything else preserved\nPATCH /api/tasks/123\n{ \"title\": \"Updated title\" }\n```\n\n## TypeScript Interface Patterns\n\n### Use Discriminated Unions for Variants\n\n```typescript\n// Good: Each variant is explicit\ntype TaskStatus =\n  | { type: 'pending' }\n  | { type: 'in_progress'; assignee: string; startedAt: Date }\n  | { type: 'completed'; completedAt: Date; completedBy: string }\n  | { type: 'cancelled'; reason: string; cancelledAt: Date };\n\n// Consumer gets type narrowing\nfunction getStatusLabel(status: TaskStatus): string {\n  switch (status.type) {\n    case 'pending': return 'Pending';\n    case 'in_progress': return `In progress (${status.assignee})`;\n    case 'completed': return `Done on ${status.completedAt}`;\n    case 'cancelled': return `Cancelled: ${status.reason}`;\n  }\n}\n```\n\n### Input/Output Separation\n\n```typescript\n// Input: what the caller provides\ninterface CreateTaskInput {\n  title: string;\n  description?: string;\n}\n\n// Output: what the system returns (includes server-generated fields)\ninterface Task {\n  id: string;\n  title: string;\n  description: string | null;\n  createdAt: Date;\n  updatedAt: Date;\n  createdBy: string;\n}\n```\n\n### Use Branded Types for IDs\n\n```typescript\ntype TaskId = string & { readonly __brand: 'TaskId' };\ntype UserId = string & { readonly __brand: 'UserId' };\n\n// Prevents accidentally passing a UserId where a TaskId is expected\nfunction getTask(id: TaskId): Promise<Task> { ... }\n```\n\n## Common Rationalizations\n\n| Rationalization | Reality |\n|---|---|\n| \"We'll document the API later\" | The types ARE the documentation. Define them first. |\n| \"We don't need pagination for now\" | You will the moment someone has 100+ items. Add it from the start. |\n| \"PATCH is complicated, let's just use PUT\" | PUT requires the full object every time. PATCH is what clients actually want. |\n| \"We'll version the API when we need to\" | Breaking changes without versioning break co","tagline":"Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. 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require human review before any live investment decision.","Permission surface needs review: secrets or environment access, filesystem or document access","Dependency/runtime risk: credential or environment access, network or browser surface","Permission surface: secrets or environment access, filesystem or document access"],"backward_compatible":{"trust_score_v4":{"version":"trust-score-v4","score":73,"tier":"strong","label":"Strong shortlist","summary":"Good trust signals with a few areas worth checking before rollout."}}},"trust_score_v4":{"version":"trust-score-v4","score":73,"tier":"strong","label":"Strong shortlist","summary":"Good trust signals with a few areas worth checking before rollout.","recommendedAction":"Test in a sandbox workflow and compare its install path with close alternatives.","dimensions":[{"id":"github_adoption","label":"GitHub adoption","score":100,"weight":0.13,"status":"pass","detail":"92K GitHub stars"},{"id":"repo_activity","label":"Stars/forks activity","score":100,"weight":0.08,"status":"pass","detail":"92K stars, 9.8K forks; issue activity unavailable in current metadata"},{"id":"maintenance","label":"Recent maintenance","score":100,"weight":0.14,"status":"pass","detail":"3d since push"},{"id":"license","label":"License clarity","score":86,"weight":0.09,"status":"pass","detail":"MIT"},{"id":"documentation","label":"README/SKILL.md completeness","score":86,"weight":0.14,"status":"pass","detail":"Metadata includes enough usage and workflow context"},{"id":"dependency_risk","label":"Dependency/runtime risk","score":56,"weight":0.12,"status":"warn","detail":"credential or environment access, network or browser surface"},{"id":"installability","label":"Install availability","score":92,"weight":0.1,"status":"pass","detail":"npx skills add addyosmani/agent-skills --skill api-and-interface-design"},{"id":"install_safety","label":"Install command safety","score":92,"weight":0.1,"status":"pass","detail":"standard package or runtime install path"},{"id":"permission_surface","label":"Permission surface","score":34,"weight":0.07,"status":"fail","detail":"secrets or environment access, filesystem or document access"},{"id":"repository","label":"Repository evidence","score":86,"weight":0.04,"status":"pass","detail":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design"},{"id":"review_status","label":"Review status","score":66,"weight":0.05,"status":"info","detail":"AI review data available"},{"id":"agent_outcomes","label":"Agent Proven outcomes","score":54,"weight":0.13,"status":"info","detail":"No agent outcome data yet"}],"checks":[{"status":"pass","label":"GitHub adoption","detail":"92K GitHub stars"},{"status":"pass","label":"Stars/forks activity","detail":"92K stars, 9.8K forks; 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Use Resolve, run one narrow sandbox task, then report the result.","metrics":{"totalOutcomes":0,"successfulOutcomes":0,"failedOutcomes":0,"installAttempts":0,"installSuccessRate":null,"successRate":null,"recentSuccessRate":null,"recentFailureRate":null,"riskBlocked":0,"setupRequired":0,"notRelevant":0,"avgOutputQuality":null,"avgTimeToUsefulMs":null,"productionOutcomes":0,"humanReviewRequired":0,"uniqueAgents":0,"lastOutcomeAt":null},"signals":[],"penalties":["No real agent outcome evidence yet"]},"outcome_stats":null,"safety":{"score":49,"level":"avoid_auto_install","label":"Avoid automatic install","safety_tier":{"tier":"experimental","label":"Experimental","badge":"EXPERIMENTAL","summary":"Sparse or mixed signals. Useful for discovery, but not for autonomous installation.","recommended_action":"Test manually in an isolated workspace and compare against safer alternatives.","auto_install_policy":"review","reasons":["High-risk permission hints: Secrets or environment access","49/100 agent safety score"]},"auto_install_allowed":false,"human_review_required":true,"blocked":false,"audit_risk":"needs_review","permission_hints":[{"id":"browser","label":"Browser automation","reason":"Skill may drive a browser or interact with web pages.","severity":"medium"},{"id":"network","label":"Network access","reason":"Skill likely fetches remote pages, APIs, repositories, or external services.","severity":"medium"},{"id":"filesystem","label":"Filesystem access","reason":"Skill may read or write project files, documents, generated artifacts, or local workspace state.","severity":"medium"},{"id":"secrets","label":"Secrets or environment access","reason":"Skill metadata references credentials, tokens, environment variables, or secret-bearing workflows.","severity":"high"},{"id":"database","label":"Database access","reason":"Skill may inspect schemas, query databases, or work with persistent stores.","severity":"medium"}],"policy_warnings":["High-risk permission hints: Secrets or environment access","Dependency or permission surface needs review"],"constraints_applied":{"max_risk":"medium","needs_install_command":true,"min_stars":0}},"safety_gate":{"tier":"experimental","label":"Experimental","badge":"EXPERIMENTAL","auto_install_policy":"review","auto_install_allowed":false,"blocked":false,"human_review_required":true,"recommended_action":"Test manually in an isolated workspace and compare against safer alternatives.","reasons":["High-risk permission hints: Secrets or environment access","49/100 agent safety score"]},"eval":{"version":"openagentskill-skill-eval-v1","status":"failed","score":77,"risk_level":"high","decision":{"recommendation":"do_not_auto_install","reason":"Permission surface: secrets or environment access, filesystem or document access","auto_install_allowed":false,"policy":"block","human_review_required":true},"blockers":["Permission surface: secrets or environment access, filesystem or document access"],"warnings":["Trust score: Good trust signals with a few areas worth checking before rollout.","Audit score: Needs review","Agent safety gate: Sparse or mixed signals. 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Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.","category":"design-creative","url":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design","repository":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design","github_repo":"addyosmani/agent-skills"},"suited_tasks":["Database and SQL workflows","Claude Code teams","teams that value GitHub adoption signals","Understand table relationships","Write safer queries","Explain database changes","Navigate pages","Click and type safely"],"suited_agents":["Codex","Claude Code","Cursor","OpenAgentSkill CLI","CLI"],"install":{"command":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","ready":true,"targets":[{"id":"openagentskill-cli","label":"CLI","kind":"command","value":"npx --yes https://github.com/Leon-Drq/openagentskill/releases/download/cli-v0.3.0/openagentskill-0.3.0.tgz add addyosmani-api-and-interface-design"},{"id":"codex","label":"Codex","kind":"agent-prompt","value":"Install the \"api-and-interface-design\" agent skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Read its SKILL.md or equivalent instructions first, install only the files needed for this workspace, and summarize any required setup before using it. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"codex\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes."},{"id":"claude-code","label":"Claude Code","kind":"agent-prompt","value":"Add \"api-and-interface-design\" as a Claude Code skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Inspect the skill instructions, place the reusable skill files in the appropriate local skills location for this project, and report the activation steps. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"claude-code\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes."},{"id":"cursor","label":"Cursor","kind":"agent-prompt","value":"Turn \"api-and-interface-design\" from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design into a reusable Cursor project rule or agent instruction. Preserve the core workflow, adapt paths to this repo, and keep the rule scoped to tasks where it is relevant. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"cursor\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. 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Use Resolve, run one narrow sandbox task, then report the result.","metrics":{"totalOutcomes":0,"successfulOutcomes":0,"failedOutcomes":0,"installAttempts":0,"installSuccessRate":null,"successRate":null,"recentSuccessRate":null,"recentFailureRate":null,"riskBlocked":0,"setupRequired":0,"notRelevant":0,"avgOutputQuality":null,"avgTimeToUsefulMs":null,"productionOutcomes":0,"humanReviewRequired":0,"uniqueAgents":0,"lastOutcomeAt":null},"signals":[],"penalties":["No real agent outcome evidence yet"]},"audit":{"score":85,"risk_level":"needs_review","risk_label":"Needs review","warnings":["Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary.","The cross-reference to 'deprecation-and-migration' is not included, which could be a broken reference if that skill is not available in the target environment.","The provided excerpt cuts off in the 'Prefer Addition Over Modification' section; the submitted SKILL.md should be verified to ensure all sections are complete.","Financial research output is not financial advice; require human review before any live investment decision."]},"safety_gate":{"tier":"experimental","label":"Experimental","auto_install_policy":"review","auto_install_allowed":false,"human_review_required":true,"blocked":false,"recommended_action":"Test manually in an isolated workspace and compare against safer alternatives."},"quality":{"score":95,"label":"Excellent"},"supply":{"track":"Coding and developer agents","scenario":"Database and SQL","maintenance":"3d since push","risk":"Needs review"},"alternative_skills":[],"do_not_use_when":["teams that need a vendor-supported SLA","production agents without a repository review","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","High-risk permission hints: Secrets or environment access","Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary."],"agent_contract":{"task_input":"Use api-and-interface-design in an agent workflow","recommended_action":"Test manually in an isolated workspace and compare against safer alternatives.","install_policy":"review","minimum_review_before_use":["Trust: 73/100 Strong shortlist","Audit: 85/100 Needs review","Safety: 49/100 Avoid automatic install","Review repository, license, install command, and permission surface before production use."],"expected_agent_output":{"selected_skill":"addyosmani-api-and-interface-design (api-and-interface-design)","install_command":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","risk_summary":"Needs review; Experimental; Review before production","verification_result":"Report the smallest successful task, files touched, warnings, and any missing setup."}},"outcome_feedback":{"endpoint":"https://www.openagentskill.com/api/agent/outcome","method":"POST","requires_resolve_event_id":true,"event_id_source":"Use install_receipt.outcome_feedback.event_id or feedback.event_id returned by /api/agent/resolve for the current task.","expected_outcomes":["success","failed","not_relevant","blocked_by_risk","setup_required"],"payload_template":{"event_id":"<install_receipt.outcome_feedback.event_id or feedback.event_id from /api/agent/resolve>","skill_slug":"addyosmani-api-and-interface-design","task":"Use api-and-interface-design in an agent workflow","agent":"codex","outcome":"success","install_used":true,"risk_blocked":false,"setup_required":false,"task_success":true,"output_quality":4,"error_type":null,"human_review_required":false,"workspace":"sandbox","time_to_useful_ms":120000,"notes":"Report the smallest successful task, setup friction, files touched, and risk notes."}},"endpoints":{"web":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design","api":"https://www.openagentskill.com/api/agent/skills/addyosmani-api-and-interface-design","audit":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design/audit","eval":"https://www.openagentskill.com/api/agent/evals?slug=addyosmani-api-and-interface-design&task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&max_risk=medium","resolve":"https://www.openagentskill.com/api/agent/resolve?task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&agent=codex&max_risk=medium","receipt":"https://www.openagentskill.com/api/agent/receipt?task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&agent=codex&max_risk=medium&format=text","install":"https://www.openagentskill.com/api/skills/addyosmani-api-and-interface-design/install","manifest":"https://www.openagentskill.com/api/registry/manifest/addyosmani-api-and-interface-design"}},"machine_metadata":{"version":"openagentskill-agent-metadata-v2","skill":{"slug":"addyosmani-api-and-interface-design","name":"api-and-interface-design","description":"Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend.","category":"design-creative","url":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design","repository":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design","github_repo":"addyosmani/agent-skills"},"suited_tasks":["Database and SQL workflows","Claude Code teams","teams that value GitHub adoption signals","Understand table relationships","Write safer queries","Explain database changes","Navigate pages","Click and type safely"],"suited_agents":["Codex","Claude Code","Cursor","OpenAgentSkill CLI","CLI"],"install":{"command":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","ready":true,"targets":[{"id":"openagentskill-cli","label":"CLI","kind":"command","value":"npx --yes https://github.com/Leon-Drq/openagentskill/releases/download/cli-v0.3.0/openagentskill-0.3.0.tgz add addyosmani-api-and-interface-design"},{"id":"codex","label":"Codex","kind":"agent-prompt","value":"Install the \"api-and-interface-design\" agent skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Read its SKILL.md or equivalent instructions first, install only the files needed for this workspace, and summarize any required setup before using it. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"codex\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes."},{"id":"claude-code","label":"Claude Code","kind":"agent-prompt","value":"Add \"api-and-interface-design\" as a Claude Code skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Inspect the skill instructions, place the reusable skill files in the appropriate local skills location for this project, and report the activation steps. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"claude-code\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes."},{"id":"cursor","label":"Cursor","kind":"agent-prompt","value":"Turn \"api-and-interface-design\" from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design into a reusable Cursor project rule or agent instruction. Preserve the core workflow, adapt paths to this repo, and keep the rule scoped to tasks where it is relevant. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"cursor\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes."}],"handoff_url":"https://www.openagentskill.com/api/skills/addyosmani-api-and-interface-design/install","manifest_url":"https://www.openagentskill.com/api/registry/manifest/addyosmani-api-and-interface-design"},"trust":{"score":73,"label":"Strong shortlist","version":"trust-score-v4","install_policy":"human_review_before_install","evidence":{"stars":"92K GitHub stars","repoActivity":"92K stars, 9.8K forks","lastPushed":"3d since push","license":"MIT","repository":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design","install":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","installSafety":"standard package or runtime install path","permissionSurface":"secrets or environment access, filesystem or document access","documentation":"Strong README/SKILL.md context","agentOutcomes":"No agent outcome data yet"},"outcome_evidence":{"total":0,"successes":0,"failures":0,"not_relevant":0,"success_rate":null,"recent_success_rate":null,"recent_failure_rate":null,"install_attempts":0,"install_success_rate":null,"risk_blocked":0,"setup_required":0,"avg_output_quality":null,"production_outcomes":0,"last_outcome_at":null,"label":"No agent outcome data yet"},"auto_install":{"allowed":false,"sandbox_required":true,"reason":"Human review or sandbox validation is required before automatic installation."},"best_for":["design-creative","agent-skill"],"known_risks":["SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","Financial research output is not financial advice; require human review before any live investment decision.","Permission surface needs review: secrets or environment access, filesystem or document access","Dependency/runtime risk: credential or environment access, network or browser surface","Permission surface: secrets or environment access, filesystem or document access"]},"agent_proven":{"version":"agent-proven-v1","score":0,"tier":"unproven","label":"Needs first agent run","summary":"No agent outcome reports yet. Use Resolve, run one narrow sandbox task, then report the result.","metrics":{"totalOutcomes":0,"successfulOutcomes":0,"failedOutcomes":0,"installAttempts":0,"installSuccessRate":null,"successRate":null,"recentSuccessRate":null,"recentFailureRate":null,"riskBlocked":0,"setupRequired":0,"notRelevant":0,"avgOutputQuality":null,"avgTimeToUsefulMs":null,"productionOutcomes":0,"humanReviewRequired":0,"uniqueAgents":0,"lastOutcomeAt":null},"signals":[],"penalties":["No real agent outcome evidence yet"]},"audit":{"score":85,"risk_level":"needs_review","risk_label":"Needs review","warnings":["Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary.","The cross-reference to 'deprecation-and-migration' is not included, which could be a broken reference if that skill is not available in the target environment.","The provided excerpt cuts off in the 'Prefer Addition Over Modification' section; the submitted SKILL.md should be verified to ensure all sections are complete.","Financial research output is not financial advice; require human review before any live investment decision."]},"safety_gate":{"tier":"experimental","label":"Experimental","auto_install_policy":"review","auto_install_allowed":false,"human_review_required":true,"blocked":false,"recommended_action":"Test manually in an isolated workspace and compare against safer alternatives."},"quality":{"score":95,"label":"Excellent"},"supply":{"track":"Coding and developer agents","scenario":"Database and SQL","maintenance":"3d since push","risk":"Needs review"},"alternative_skills":[],"do_not_use_when":["teams that need a vendor-supported SLA","production agents without a repository review","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","High-risk permission hints: Secrets or environment access","Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary."],"agent_contract":{"task_input":"Use api-and-interface-design in an agent workflow","recommended_action":"Test manually in an isolated workspace and compare against safer alternatives.","install_policy":"review","minimum_review_before_use":["Trust: 73/100 Strong shortlist","Audit: 85/100 Needs review","Safety: 49/100 Avoid automatic install","Review repository, license, install command, and permission surface before production use."],"expected_agent_output":{"selected_skill":"addyosmani-api-and-interface-design (api-and-interface-design)","install_command":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","risk_summary":"Needs review; Experimental; Review before production","verification_result":"Report the smallest successful task, files touched, warnings, and any missing setup."}},"outcome_feedback":{"endpoint":"https://www.openagentskill.com/api/agent/outcome","method":"POST","requires_resolve_event_id":true,"event_id_source":"Use install_receipt.outcome_feedback.event_id or feedback.event_id returned by /api/agent/resolve for the current task.","expected_outcomes":["success","failed","not_relevant","blocked_by_risk","setup_required"],"payload_template":{"event_id":"<install_receipt.outcome_feedback.event_id or feedback.event_id from /api/agent/resolve>","skill_slug":"addyosmani-api-and-interface-design","task":"Use api-and-interface-design in an agent workflow","agent":"codex","outcome":"success","install_used":true,"risk_blocked":false,"setup_required":false,"task_success":true,"output_quality":4,"error_type":null,"human_review_required":false,"workspace":"sandbox","time_to_useful_ms":120000,"notes":"Report the smallest successful task, setup friction, files touched, and risk notes."}},"endpoints":{"web":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design","api":"https://www.openagentskill.com/api/agent/skills/addyosmani-api-and-interface-design","audit":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design/audit","eval":"https://www.openagentskill.com/api/agent/evals?slug=addyosmani-api-and-interface-design&task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&max_risk=medium","resolve":"https://www.openagentskill.com/api/agent/resolve?task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&agent=codex&max_risk=medium","receipt":"https://www.openagentskill.com/api/agent/receipt?task=Use%20api-and-interface-design%20in%20an%20agent%20workflow&agent=codex&max_risk=medium&format=text","install":"https://www.openagentskill.com/api/skills/addyosmani-api-and-interface-design/install","manifest":"https://www.openagentskill.com/api/registry/manifest/addyosmani-api-and-interface-design"}},"supply_profile":{"track":{"slug":"coding","label":"Coding and developer agents","shortLabel":"Coding","description":"Code review, repo analysis, testing, CI, GitHub, DevOps, and developer workflow skills."},"scenario":{"label":"Database and SQL","description":"I need my agent to inspect database schemas, write SQL, and explain query results.","useCases":[{"slug":"database-sql","title":"Database and SQL"},{"slug":"browser-automation","title":"Browser automation"},{"slug":"document-processing","title":"Document processing"}]},"applicableAgents":["Claude Code","CLI","Codex","Cursor"],"install":{"ready":true,"command":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","primaryTarget":"CLI","targetCount":4},"githubQuality":{"stars":92201,"starsLabel":"92K","forks":9827,"license":"MIT","qualityScore":95,"trustScore":73,"auditScore":85},"maintenance":{"status":"fresh","label":"3d since push","daysSincePush":3,"lastPushedAt":"2026-09-04T06:45:55+00:00"},"risk":{"level":"needs_review","label":"Needs review","requiresReview":true,"notes":["Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary."]},"coverageTags":["Coding","Database and SQL","design-creative","agent-skill"]},"audit":{"audit_score":85,"risk_level":"needs_review","risk_label":"Needs review","quality_score":95,"trust_score":73,"maintenance_score":100,"security_score":74,"install_score":92,"warnings":["Dependency or permission surface needs review","Permission surface may require sandboxing","Financial research output is not financial advice; require human review before any live investment decision","SKILL.md is documentation-style and does not define an explicit step-by-step workflow or inputs/outputs, so an agent must infer how to apply the principles in practice.","No 'When not to use' or 'Limitations' section; the skill may be over-applied to internal implementation details where rigid API contract practices are unnecessary.","The cross-reference to 'deprecation-and-migration' is not included, which could be a broken reference if that skill is not available in the target environment.","The provided excerpt cuts off in the 'Prefer Addition Over Modification' section; the submitted SKILL.md should be verified to ensure all sections are complete.","Financial research output is not financial advice; require human review before any live investment decision.","Permission surface needs review: secrets or environment access, filesystem or document access","Dependency/runtime risk: credential or environment access, network or browser surface","Permission surface: secrets or environment access, filesystem or document access"]},"quality_signals":{"model":"v2","star_score":34.75,"usage_score":0,"review_score":4.8,"metadata_score":3,"freshness_score":15},"platforms":["Claude Code"],"use_cases":[{"slug":"database-sql","title":"Database and SQL","url":"https://www.openagentskill.com/use-cases/database-sql"},{"slug":"browser-automation","title":"Browser automation","url":"https://www.openagentskill.com/use-cases/browser-automation"},{"slug":"document-processing","title":"Document processing","url":"https://www.openagentskill.com/use-cases/document-processing"},{"slug":"testing-qa","title":"Testing and QA","url":"https://www.openagentskill.com/use-cases/testing-qa"}],"stacks":[{"slug":"browser-qa-agent","title":"Browser QA agent","url":"https://www.openagentskill.com/collections/browser-qa-agent"},{"slug":"frontend-product-ui","title":"Frontend and UI","url":"https://www.openagentskill.com/collections/frontend-product-ui"},{"slug":"content-growth-agent","title":"Content growth agent","url":"https://www.openagentskill.com/collections/content-growth-agent"}],"install":"npx skills add addyosmani/agent-skills --skill api-and-interface-design","install_targets":[{"id":"openagentskill-cli","label":"CLI","title":"OpenAgentSkill CLI","kind":"command","value":"npx --yes https://github.com/Leon-Drq/openagentskill/releases/download/cli-v0.3.0/openagentskill-0.3.0.tgz add addyosmani-api-and-interface-design","description":"Resolve policy, run the source installer safely, and report a verified install receipt.","copyLabel":"Copy command"},{"id":"codex","label":"Codex","title":"Codex install prompt","kind":"agent-prompt","value":"Install the \"api-and-interface-design\" agent skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Read its SKILL.md or equivalent instructions first, install only the files needed for this workspace, and summarize any required setup before using it. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"codex\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes.","description":"Give Codex a repo-aware install prompt when the skill is not available through a local CLI.","copyLabel":"Copy prompt"},{"id":"claude-code","label":"Claude Code","title":"Claude Code skill prompt","kind":"agent-prompt","value":"Add \"api-and-interface-design\" as a Claude Code skill from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design. Inspect the skill instructions, place the reusable skill files in the appropriate local skills location for this project, and report the activation steps. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"claude-code\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes.","description":"Use this prompt to ask Claude Code to add the skill and explain the local activation steps.","copyLabel":"Copy prompt"},{"id":"cursor","label":"Cursor","title":"Cursor rule prompt","kind":"agent-prompt","value":"Turn \"api-and-interface-design\" from https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design into a reusable Cursor project rule or agent instruction. Preserve the core workflow, adapt paths to this repo, and keep the rule scoped to tasks where it is relevant. Skill purpose: Guides stable API and interface design. Use when designing APIs, module boundaries, or any public interface. Use when creating REST or GraphQL endpoints, defining type contracts between modules, or establishing boundaries between frontend and backend. After the install attempt, report the result to https://www.openagentskill.com/api/agent/outcome with POST JSON {\"event_id\":\"install_<unique-id>\",\"skill_slug\":\"addyosmani-api-and-interface-design\",\"task\":\"Install api-and-interface-design\",\"agent\":\"cursor\",\"outcome\":\"success\",\"install_used\":true}. Replace event_id with a unique value and outcome with success or failed. Report success only after the skill is installed and a minimal verification passes.","description":"Use this when installing as Cursor project rules or reusable agent instructions.","copyLabel":"Copy prompt"}],"repository":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design","github_repo":"addyosmani/agent-skills","version":"1.0.0","license":"MIT","urls":{"web":"https://www.openagentskill.com/skills/addyosmani-api-and-interface-design","repository":"https://github.com/addyosmani/agent-skills/tree/main/skills/api-and-interface-design","api":"/api/agent/skills/addyosmani-api-and-interface-design","install_api":"/api/skills/addyosmani-api-and-interface-design/install"},"meta":{"created_at":"2026-08-28T13:20:46.374879+00:00","updated_at":"2026-09-04T13:23:05.685315+00:00","agent_friendly":true}}