--- name: simple-english description: | Write or rewrite text in plain, layman-readable English in the spirit of ASD-STE100 Simplified Technical English: short sentences, active voice, simple tenses, one word one meaning, condition before command, every technical term defined at first use, no AI slop. Default mode is Plain. Strict mode applies full STE vocabulary compliance when the user names STE, ASD-STE100, or compliance. Use for documentation, READMEs, runbooks, procedures, error messages, release notes, incident reports, API guides, and explanations for readers outside the field. Also use when the user says "STE", "Simplified Technical English", "ASD-STE100", "plain English", "layman's terms", "explain it simply", "no jargon", "de-slop", "make this readable", "write for non-native readers", or asks for docs that translate well. The same rules govern the reply: answer first, five sentences or fewer. license: MIT compatibility: claude-code cursor codex gemini-cli opencode metadata: version: "2.0.0" standard: ASD-STE100 Issue 9 (2025-01-15) ---

# Simple English: Plain Words, Aerospace Discipline

Write plain English that a smart reader outside your field understands on one read. The rules come from ASD-STE100, the controlled language aerospace uses so a tired mechanic cannot misread an instruction. They also remove the signs of AI writing: long sentences, synonym rotation, hedges, filler. Each sentence must survive one read.

## Your Task

When asked to write or rewrite text:

1. **Select the mode** (Plain or Strict, the table that follows). In Strict mode, read `references/strict-vocabulary.md` before you draft. 2. **Classify each passage** as procedural or descriptive. Every other rule depends on this. 3. **Fix your vocabulary before you draft.** Use `make sure that` for check/verify/confirm/validate/ensure as verbs, and `configuration` for config/settings/options. Use no other word for these concepts in the whole document. 4. **Define a technical term at its first use** when a reader outside the field needs it: concept words, not product names or the tool the document is about. 5. **Apply the catalog** that follows. For replies and explanations for outsiders, apply the Plain English rules first. 6. **Do the self-check** before you deliver. This step is not optional. 7. **Never touch code**, identifiers, commands, or quoted errors (see Untouchables).

When asked to CHECK text instead of writing it, report each violation as: rule number, the offending text, a compliant rewrite. Cite only rule numbers that exist in this file, never from memory: invented rule numbers are a known failure.

## Two Modes

| Mode | When | What you apply | |---|---|---| | **Plain** (default) | The user wants clear text: docs, READMEs, error messages, answers | Every structural rule in the catalog. Domain words stay ("idempotent", "webhook"). Replies and explanations for outsiders also get the Plain English rules. | | **Strict** | The user names STE, ASD-STE100, or compliance | Plain mode plus the dictionary discipline in `references/strict-vocabulary.md`. Document only: the reply to the user stays Plain. |

## Step 1: Classify the Text

| | Procedural (instructions) | Descriptive (explanations) | |---|---|---| | Purpose | Tell the reader what to do | Explain what a thing is or does | | Verb form | Imperative: "Install the pump." | Simple present/past/future | | Sentence limit | **20 words** (Rule 5.1) | **25 words** (Rule 6.3) | | Unit rule | One instruction per sentence (5.2) | One topic per paragraph (6.5), max six sentences per paragraph (6.6) |

Do not mix the two in one passage. A "Getting started" section is procedural: headed, numbered where steps follow each other, imperative. An "Architecture" section is descriptive.

## Plain English for Readers Outside the Field

Apply these six rules to your reply to the user and to explanations written for readers outside the field. Procedures and reference documents follow the catalog alone: the catalog measured best there, and these rules dilute it.

1. **Common word over jargon.** When a plain word exists, use it: "use" not "utilize", "start" not "initiate", "help" not "facilitate". `references/word-swaps.md` has the map. 2. **Define a technical term at its first use when the reader needs it.** The reader is smart and outside your field, but the document sets what they already know: do not define the tool the document is about, product names, or standard names (Postgres, S3, HTTP, JSON). Define the concept words: "idempotent (safe to run twice)", "a webhook (an HTTP call sent when an event occurs)". Keep a definition under ten words, at most one per sentence. If it pushes the sentence over the limit, give the definition its own sentence. Never use a synonym of a chosen term inside a definition (Rule 1.11). 3. **Address the reader as "you" and name the actor.** Every sentence says who does what (Rule 3.6): "You run the migration. The database rebuilds the table." 4. **Lead with the point.** The first sentence of a section, and of a reply, states the result or what the reader must do. Explanation follows. 5. **One idea per sentence, one topic per paragraph** (Rules 5.2, 6.1, 6.5). 6. **Say what is true, not how important it is.** "The cache expires after 60 seconds", not "It is crucial to note that the cache expires".

**Before:** To facilitate onboarding, it is crucial that users initiate the idempotent sync prior to configuration. **After:** Before you configure the client, start the sync. The sync is idempotent (you can run it again without side effects).

## THE RULE CATALOG

53 rules in 9 sections, paraphrased from ASD-STE100 Issue 9 with software examples. Rules marked (S) are Strict mode only (see `references/strict-vocabulary.md`). The official wording is in the free standard at asd-ste100.org.

### Section 1 — Words (Rules 1.1-1.14)

| Rule | Instruction | |---|---| | 1.1-1.4, 1.6 (S) | Use only approved words, as their listed part of speech, meaning, and form. | | 1.5 | You can use domain words as technical nouns ("webhook", "commit", "endpoint"). | | 1.7 | Do not use technical nouns as verbs. | | 1.8 | Use the technical nouns of your project or industry. | | 1.9 | When you pick a technical noun, pick a short and clear one. | | 1.10 | No regional, slang, or jargon words as technical nouns. | | 1.11 | One item, one name. Do not call it "config" here and "settings" there. | | 1.12 | You can use domain verbs as technical verbs ("deploy", "compile", "merge"). The standard names computer verbs as legal: click, type, copy, paste, delete, save, install, download, update, and more. When a common verb does the same job, prefer it: "find" instead of "detect". | | 1.13 | Do not use technical verbs as nouns. | | 1.14 | Use American English spelling. |

In Plain mode, rules 1.5, 1.8, and 1.12 make your domain vocabulary legal. The ones agents break are 1.7, 1.11, and 1.13.

**Before:** You can webhook the event, then do a deploy. **After:** Send the event to the webhook. Then deploy the service.

### Section 2 — Multi-word nouns (Rules 2.1-2.2)

| Rule | Instruction | |---|---| | 2.1 | Write multi-word nouns of three words or fewer. | | 2.2 | When a technical noun needs more than three words, write it in full once, then give a short form or hyphenate the units. |

Break long noun chains with prepositions (of, on, in, for):

**Before:** the connection pool timeout configuration value **After:** the timeout value for the connection pool

### Section 3 — Verbs (Rules 3.1-3.7)

| Rule | Instruction | |---|---| | 3.1 (S) | Use only the verb forms that the dictionary gives. | | 3.2 | Use only: infinitive, imperative, simple present, simple past, simple future, past participle as adjective. | | 3.3 | Use the past participle only as an adjective ("the cached response"). | | 3.4 | No auxiliary verbs for complex constructions. No present perfect, no "is to be installed". | | 3.5 | Use an "-ing" form only as a technical noun or inside one ("logging", "the mounting bracket"), never as a verb. | | 3.6 | Active voice. In descriptive text, passive is legal only when the agent is unknown. To repair an agentless passive, use "you" (the reader) or "we" (your company): "Indexes are not used on this table" → "We do not use indexes on this table." | | 3.7 | Describe an action with a verb, not a noun ("compress the file", not "perform compression of the file"). |

**Approved modals: can, will, must. Banned: should, would, may, might, could.** The standard rejects "could" even for possibility: write "an explosion can occur", never "could occur". For "should": a requirement becomes "must". A suggestion is stated as fact or deleted. This matters double for agent instructions, because models read "should" as optional.

**Before:** The migration has completed and the table is being rebuilt. **After:** The migration completed. The database rebuilds the table.

### Section 4 — Sentences (Rules 4.1-4.5)

| Rule | Instruction | |---|---| | 4.1 | Write short and clear sentences. | | 4.2 | Do not omit words or use contractions to shorten sentences. Keep articles, keep "that". | | 4.3 | Use a vertical list for complex text: colon on the lead-in, uppercase start, a period only on full-sentence items, no mixed instructions and facts, no nesting. | | 4.4 | Use connecting words between sentences on related topics ("Then", "As a result"). | | 4.5 | Put an article (the, a, an) or a demonstrative adjective (this, these) before nouns where applicable. Exception: no article before a noun when an identifier follows it: "Restart pod web-7f9b2". |

Rule 4.2 is the anti-terseness rule. Plain English is short sentences with complete grammar, not telegraph style:

**Wrong shortening:** Ensure file exists before running. **Plain:** Make sure that the file exists before you run the command.

### Section 5 — Procedural writing (Rules 5.1-5.5)

| Rule | Instruction | |---|---| | 5.1 | Maximum 20 words per sentence. Warnings and cautions included. | | 5.2 | One instruction per sentence, unless two actions happen at the same time. A step can add one sentence for an immediate result or limit. | | 5.3 | Write instructions in the imperative: "Run the migration." | | 5.4 | Put a required condition before the command, divided by a comma: "If the build fails, read the log." | | 5.5 | Notes give information, never instructions or limits. A limit belongs with its action. Notes test: the procedure must still work for a reader who deletes all notes. |

**Before:** You'll want to grab the API key from the dashboard before configuring the client, which you can do under Settings. **After:** Get the API key from the dashboard, under Settings. Then configure the client with this key.

### Section 6 — Descriptive writing (Rules 6.1-6.6)

| Rule | Instruction | |---|---| | 6.1 | Give information gradually: one new fact per sentence. | | 6.2 | Use key words and phrases to give the text a logical structure. | | 6.3 | Maximum 25 words per sentence. | | 6.4 | Group related information in paragraphs. | | 6.5 | One topic per paragraph. | | 6.6 | Maximum six sentences per paragraph. |

No imperative in descriptive text. Descriptions explain. Procedures instruct.

### Section 7 — Safety instructions (Rules 7.1-7.3)

| Rule | Instruction | |---|---| | 7.1 | Use a word that shows the risk level ("WARNING" = injury, "CAUTION" = damage). If the two risks occur together, use "WARNING". | | 7.2 | Start with a clear command or condition. | | 7.3 | Then give the risk or the possible result. |

Never bury the instruction after the explanation. The same pattern fits destructive CLI flags and irreversible migrations.

**Before:** Note that data loss may occur in some circumstances if the destructive flag happens to be enabled when running against production. **After:** CAUTION: Do not use the `--force` flag against production. The flag deletes rows that do not match the source.

### Section 8 — Punctuatio

--- name: simple-english description: | Write or rewrite text in plain, layman-readable English in the spirit of ASD-STE100 Simplified Technical English: short sentences, active voice, simple tenses, one word one meaning, condition before command, every technical term defined at first use, no AI slop. Default mode is Plain. Strict mode applies full STE vocabulary compliance when the user names STE, ASD-STE100, or compliance. Use for documentation, READMEs, runbooks, procedures, error messages, release notes, incident reports, API guides, and explanations for readers outside the field. Also use when the user says "STE", "Simplified Technical English", "ASD-STE100", "plain English", "layman's terms", "explain it simply", "no jargon", "de-slop", "make this readable", "write for non-native readers", or asks for docs that translate well. The same rules govern the reply: answer first, five sentences or fewer. license: MIT compatibility: claude-code cursor codex gemini-cli opencode metadata: version: "2.0.0" standard: ASD-STE100 Issue 9 (2025-01-15) ---

# Simple English: Plain Words, Aerospace Discipline

Write plain English that a smart reader outside your field understands on one read. The rules come from ASD-STE100, the controlled language aerospace uses so a tired mechanic cannot misread an instruction. They also remove the signs of AI writing: long sentences, synonym rotation, hedges, filler. Each sentence must survive one read.

## Your Task

When asked to write or rewrite text:

1. **Select the mode** (Plain or Strict, the table that follows). In Strict mode, read `references/strict-vocabulary.md` before you draft. 2. **Classify each passage** as procedural or descriptive. Every other rule depends on this. 3. **Fix your vocabulary before you draft.** Use `make sure that` for check/verify/confirm/validate/ensure as verbs, and `configuration` for config/settings/options. Use no other word for these concepts in the whole document. 4. **Define a technical term at its first use** when a reader outside the field needs it: concept words, not product names or the tool the document is about. 5. **Apply the catalog** that follows. For replies and explanations for outsiders, apply the Plain English rules first. 6. **Do the self-check** before you deliver. This step is not optional. 7. **Never touch code**, identifiers, commands, or quoted errors (see Untouchables).

When asked to CHECK text instead of writing it, report each violation as: rule number, the offending text, a compliant rewrite. Cite only rule numbers that exist in this file, never from memory: invented rule numbers are a known failure.

## Two Modes

| Mode | When | What you apply | |---|---|---| | **Plain** (default) | The user wants clear text: docs, READMEs, error messages, answers | Every structural rule in the catalog. Domain words stay ("idempotent", "webhook"). Replies and explanations for outsiders also get the Plain English rules. | | **Strict** | The user names STE, ASD-STE100, or compliance | Plain mode plus the dictionary discipline in `references/strict-vocabulary.md`. Document only: the reply to the user stays Plain. |

## Step 1: Classify the Text

| | Procedural (instructions) | Descriptive (explanations) | |---|---|---| | Purpose | Tell the reader what to do | Explain what a thing is or does | | Verb form | Imperative: "Install the pump." | Simple present/past/future | | Sentence limit | **20 words** (Rule 5.1) | **25 words** (Rule 6.3) | | Unit rule | One instruction per sentence (5.2) | One topic per paragraph (6.5), max six sentences per paragraph (6.6) |

Do not mix the two in one passage. A "Getting started" section is procedural: headed, numbered where steps follow each other, imperative. An "Architecture" section is descriptive.

## Plain English for Readers Outside the Field

Apply these six rules to your reply to the user and to explanations written for readers outside the field. Procedures and reference documents follow the catalog alone: the catalog measured best there, and these rules dilute it.

1. **Common word over jargon.** When a plain word exists, use it: "use" not "utilize", "start" not "initiate", "help" not "facilitate". `references/word-swaps.md` has the map. 2. **Define a technical term at its first use when the reader needs it.** The reader is smart and outside your field, but the document sets what they already know: do not define the tool the document is about, product names, or standard names (Postgres, S3, HTTP, JSON). Define the concept words: "idempotent (safe to run twice)", "a webhook (an HTTP call sent when an event occurs)". Keep a definition under ten words, at most one per sentence. If it pushes the sentence over the limit, give the definition its own sentence. Never use a synonym of a chosen term inside a definition (Rule 1.11). 3. **Address the reader as "you" and name the actor.** Every sentence says who does what (Rule 3.6): "You run the migration. The database rebuilds the table." 4. **Lead with the point.** The first sentence of a section, and of a reply, states the result or what the reader must do. Explanation follows. 5. **One idea per sentence, one topic per paragraph** (Rules 5.2, 6.1, 6.5). 6. **Say what is true, not how important it is.** "The cache expires after 60 seconds", not "It is crucial to note that the cache expires".

**Before:** To facilitate onboarding, it is crucial that users initiate the idempotent sync prior to configuration. **After:** Before you configure the client, start the sync. The sync is idempotent (you can run it again without side effects).

## THE RULE CATALOG

53 rules in 9 sections, paraphrased from ASD-STE100 Issue 9 with software examples. Rules marked (S) are Strict mode only (see `references/strict-vocabulary.md`). The official wording is in the free standard at asd-ste100.org.

### Section 1 — Words (Rules 1.1-1.14)

| Rule | Instruction | |---|---| | 1.1-1.4, 1.6 (S) | Use only approved words, as their listed part of speech, meaning, and form. | | 1.5 | You can use domain words as technical nouns ("webhook", "commit", "endpoint"). | | 1.7 | Do not use technical nouns as verbs. | | 1.8 | Use the technical nouns of your project or industry. | | 1.9 | When you pick a technical noun, pick a short and clear one. | | 1.10 | No regional, slang, or jargon words as technical nouns. | | 1.11 | One item, one name. Do not call it "config" here and "settings" there. | | 1.12 | You can use domain verbs as technical verbs ("deploy", "compile", "merge"). The standard names computer verbs as legal: click, type, copy, paste, delete, save, install, download, update, and more. When a common verb does the same job, prefer it: "find" instead of "detect". | | 1.13 | Do not use technical verbs as nouns. | | 1.14 | Use American English spelling. |

In Plain mode, rules 1.5, 1.8, and 1.12 make your domain vocabulary legal. The ones agents break are 1.7, 1.11, and 1.13.

**Before:** You can webhook the event, then do a deploy. **After:** Send the event to the webhook. Then deploy the service.

### Section 2 — Multi-word nouns (Rules 2.1-2.2)

| Rule | Instruction | |---|---| | 2.1 | Write multi-word nouns of three words or fewer. | | 2.2 | When a technical noun needs more than three words, write it in full once, then give a short form or hyphenate the units. |

Break long noun chains with prepositions (of, on, in, for):

**Before:** the connection pool timeout configuration value **After:** the timeout value for the connection pool

### Section 3 — Verbs (Rules 3.1-3.7)

| Rule | Instruction | |---|---| | 3.1 (S) | Use only the verb forms that the dictionary gives. | | 3.2 | Use only: infinitive, imperative, simple present, simple past, simple future, past participle as adjective. | | 3.3 | Use the past participle only as an adjective ("the cached response"). | | 3.4 | No auxiliary verbs for complex constructions. No present perfect, no "is to be installed". | | 3.5 | Use an "-ing" form only as a technical noun or inside one ("logging", "the mounting bracket"), never as a verb. | | 3.6 | Active voice. In descriptive text, passive is legal only when the agent is unknown. To repair an agentless passive, use "you" (the reader) or "we" (your company): "Indexes are not used on this table" → "We do not use indexes on this table." | | 3.7 | Describe an action with a verb, not a noun ("compress the file", not "perform compression of the file"). |

**Approved modals: can, will, must. Banned: should, would, may, might, could.** The standard rejects "could" even for possibility: write "an explosion can occur", never "could occur". For "should": a requirement becomes "must". A suggestion is stated as fact or deleted. This matters double for agent instructions, because models read "should" as optional.

**Before:** The migration has completed and the table is being rebuilt. **After:** The migration completed. The database rebuilds the table.

### Section 4 — Sentences (Rules 4.1-4.5)

| Rule | Instruction | |---|---| | 4.1 | Write short and clear sentences. | | 4.2 | Do not omit words or use contractions to shorten sentences. Keep articles, keep "that". | | 4.3 | Use a vertical list for complex text: colon on the lead-in, uppercase start, a period only on full-sentence items, no mixed instructions and facts, no nesting. | | 4.4 | Use connecting words between sentences on related topics ("Then", "As a result"). | | 4.5 | Put an article (the, a, an) or a demonstrative adjective (this, these) before nouns where applicable. Exception: no article before a noun when an identifier follows it: "Restart pod web-7f9b2". |

Rule 4.2 is the anti-terseness rule. Plain English is short sentences with complete grammar, not telegraph style:

**Wrong shortening:** Ensure file exists before running. **Plain:** Make sure that the file exists before you run the command.

### Section 5 — Procedural writing (Rules 5.1-5.5)

| Rule | Instruction | |---|---| | 5.1 | Maximum 20 words per sentence. Warnings and cautions included. | | 5.2 | One instruction per sentence, unless two actions happen at the same time. A step can add one sentence for an immediate result or limit. | | 5.3 | Write instructions in the imperative: "Run the migration." | | 5.4 | Put a required condition before the command, divided by a comma: "If the build fails, read the log." | | 5.5 | Notes give information, never instructions or limits. A limit belongs with its action. Notes test: the procedure must still work for a reader who deletes all notes. |

**Before:** You'll want to grab the API key from the dashboard before configuring the client, which you can do under Settings. **After:** Get the API key from the dashboard, under Settings. Then configure the client with this key.

### Section 6 — Descriptive writing (Rules 6.1-6.6)

| Rule | Instruction | |---|---| | 6.1 | Give information gradually: one new fact per sentence. | | 6.2 | Use key words and phrases to give the text a logical structure. | | 6.3 | Maximum 25 words per sentence. | | 6.4 | Group related information in paragraphs. | | 6.5 | One topic per paragraph. | | 6.6 | Maximum six sentences per paragraph. |

No imperative in descriptive text. Descriptions explain. Procedures instruct.

### Section 7 — Safety instructions (Rules 7.1-7.3)

| Rule | Instruction | |---|---| | 7.1 | Use a word that shows the risk level ("WARNING" = injury, "CAUTION" = damage). If the two risks occur together, use "WARNING". | | 7.2 | Start with a clear command or condition. | | 7.3 | Then give the risk or the possible result. |

Never bury the instruction after the explanation. The same pattern fits destructive CLI flags and irreversible migrations.

**Before:** Note that data loss may occur in some circumstances if the destructive flag happens to be enabled when running against production. **After:** CAUTION: Do not use the `--force` flag against production. The flag deletes rows that do not match the source.

### Section 8 — Punctuatio

--- name: simple-english description: | Write or rewrite text in plain, layman-readable English in the spirit of ASD-STE100 Simplified Technical English: short sentences, active voice, simple tenses, one word one meaning, condition before command, every technical term defined at first use, no AI slop. Default mode is Plain. Strict mode applies full STE vocabulary compliance when the user names STE, ASD-STE100, or compliance. Use for documentation, READMEs, runbooks, procedures, error messages, release notes, incident reports, API guides, and explanations for readers outside the field. Also use when the user says "STE", "Simplified Technical English", "ASD-STE100", "plain English", "layman's terms", "explain it simply", "no jargon", "de-slop", "make this readable", "write for non-native readers", or asks for docs that translate well. The same rules govern the reply: answer first, five sentences or fewer. license: MIT compatibility: claude-code cursor codex gemini-cli opencode metadata: version: "2.0.0" standard: ASD-STE100 Issue 9 (2025-01-15) ---

# Simple English: Plain Words, Aerospace Discipline

Write plain English that a smart reader outside your field understands on one read. The rules come from ASD-STE100, the controlled language aerospace uses so a tired mechanic cannot misread an instruction. They also remove the signs of AI writing: long sentences, synonym rotation, hedges, filler. Each sentence must survive one read.

## Your Task

When asked to write or rewrite text:

1. **Select the mode** (Plain or Strict, the table that follows). In Strict mode, read `references/strict-vocabulary.md` before you draft. 2. **Classify each passage** as procedural or descriptive. Every other rule depends on this. 3. **Fix your vocabulary before you draft.** Use `make sure that` for check/verify/confirm/validate/ensure as verbs, and `configuration` for config/settings/options. Use no other word for these concepts in the whole document. 4. **Define a technical term at its first use** when a reader outside the field needs it: concept words, not product names or the tool the document is about. 5. **Apply the catalog** that follows. For replies and explanations for outsiders, apply the Plain English rules first. 6. **Do the self-check** before you deliver. This step is not optional. 7. **Never touch code**, identifiers, commands, or quoted errors (see Untouchables).

When asked to CHECK text instead of writing it, report each violation as: rule number, the offending text, a compliant rewrite. Cite only rule numbers that exist in this file, never from memory: invented rule numbers are a known failure.

## Two Modes

| Mode | When | What you apply | |---|---|---| | **Plain** (default) | The user wants clear text: docs, READMEs, error messages, answers | Every structural rule in the catalog. Domain words stay ("idempotent", "webhook"). Replies and explanations for outsiders also get the Plain English rules. | | **Strict** | The user names STE, ASD-STE100, or compliance | Plain mode plus the dictionary discipline in `references/strict-vocabulary.md`. Document only: the reply to the user stays Plain. |

## Step 1: Classify the Text

| | Procedural (instructions) | Descriptive (explanations) | |---|---|---| | Purpose | Tell the reader what to do | Explain what a thing is or does | | Verb form | Imperative: "Install the pump." | Simple present/past/future | | Sentence limit | **20 words** (Rule 5.1) | **25 words** (Rule 6.3) | | Unit rule | One instruction per sentence (5.2) | One topic per paragraph (6.5), max six sentences per paragraph (6.6) |

Do not mix the two in one passage. A "Getting started" section is procedural: headed, numbered where steps follow each other, imperative. An "Architecture" section is descriptive.

## Plain English for Readers Outside the Field

Apply these six rules to your reply to the user and to explanations written for readers outside the field. Procedures and reference documents follow the catalog alone: the catalog measured best there, and these rules dilute it.

1. **Common word over jargon.** When a plain word exists, use it: "use" not "utilize", "start" not "initiate", "help" not "facilitate". `references/word-swaps.md` has the map. 2. **Define a technical term at its first use when the reader needs it.** The reader is smart and outside your field, but the document sets what they already know: do not define the tool the document is about, product names, or standard names (Postgres, S3, HTTP, JSON). Define the concept words: "idempotent (safe to run twice)", "a webhook (an HTTP call sent when an event occurs)". Keep a definition under ten words, at most one per sentence. If it pushes the sentence over the limit, give the definition its own sentence. Never use a synonym of a chosen term inside a definition (Rule 1.11). 3. **Address the reader as "you" and name the actor.** Every sentence says who does what (Rule 3.6): "You run the migration. The database rebuilds the table." 4. **Lead with the point.** The first sentence of a section, and of a reply, states the result or what the reader must do. Explanation follows. 5. **One idea per sentence, one topic per paragraph** (Rules 5.2, 6.1, 6.5). 6. **Say what is true, not how important it is.** "The cache expires after 60 seconds", not "It is crucial to note that the cache expires".

**Before:** To facilitate onboarding, it is crucial that users initiate the idempotent sync prior to configuration. **After:** Before you configure the client, start the sync. The sync is idempotent (you can run it again without side effects).

## THE RULE CATALOG

53 rules in 9 sections, paraphrased from ASD-STE100 Issue 9 with software examples. Rules marked (S) are Strict mode only (see `references/strict-vocabulary.md`). The official wording is in the free standard at asd-ste100.org.

### Section 1 — Words (Rules 1.1-1.14)

| Rule | Instruction | |---|---| | 1.1-1.4, 1.6 (S) | Use only approved words, as their listed part of speech, meaning, and form. | | 1.5 | You can use domain words as technical nouns ("webhook", "commit", "endpoint"). | | 1.7 | Do not use technical nouns as verbs. | | 1.8 | Use the technical nouns of your project or industry. | | 1.9 | When you pick a technical noun, pick a short and clear one. | | 1.10 | No regional, slang, or jargon words as technical nouns. | | 1.11 | One item, one name. Do not call it "config" here and "settings" there. | | 1.12 | You can use domain verbs as technical verbs ("deploy", "compile", "merge"). The standard names computer verbs as legal: click, type, copy, paste, delete, save, install, download, update, and more. When a common verb does the same job, prefer it: "find" instead of "detect". | | 1.13 | Do not use technical verbs as nouns. | | 1.14 | Use American English spelling. |

In Plain mode, rules 1.5, 1.8, and 1.12 make your domain vocabulary legal. The ones agents break are 1.7, 1.11, and 1.13.

**Before:** You can webhook the event, then do a deploy. **After:** Send the event to the webhook. Then deploy the service.

### Section 2 — Multi-word nouns (Rules 2.1-2.2)

| Rule | Instruction | |---|---| | 2.1 | Write multi-word nouns of three words or fewer. | | 2.2 | When a technical noun needs more than three words, write it in full once, then give a short form or hyphenate the units. |

Break long noun chains with prepositions (of, on, in, for):

**Before:** the connection pool timeout configuration value **After:** the timeout value for the connection pool

### Section 3 — Verbs (Rules 3.1-3.7)

| Rule | Instruction | |---|---| | 3.1 (S) | Use only the verb forms that the dictionary gives. | | 3.2 | Use only: infinitive, imperative, simple present, simple past, simple future, past participle as adjective. | | 3.3 | Use the past participle only as an adjective ("the cached response"). | | 3.4 | No auxiliary verbs for complex constructions. No present perfect, no "is to be installed". | | 3.5 | Use an "-ing" form only as a technical noun or inside one ("logging", "the mounting bracket"), never as a verb. | | 3.6 | Active voice. In descriptive text, passive is legal only when the agent is unknown. To repair an agentless passive, use "you" (the reader) or "we" (your company): "Indexes are not used on this table" → "We do not use indexes on this table." | | 3.7 | Describe an action with a verb, not a noun ("compress the file", not "perform compression of the file"). |

**Approved modals: can, will, must. Banned: should, would, may, might, could.** The standard rejects "could" even for possibility: write "an explosion can occur", never "could occur". For "should": a requirement becomes "must". A suggestion is stated as fact or deleted. This matters double for agent instructions, because models read "should" as optional.

**Before:** The migration has completed and the table is being rebuilt. **After:** The migration completed. The database rebuilds the table.

### Section 4 — Sentences (Rules 4.1-4.5)

| Rule | Instruction | |---|---| | 4.1 | Write short and clear sentences. | | 4.2 | Do not omit words or use contractions to shorten sentences. Keep articles, keep "that". | | 4.3 | Use a vertical list for complex text: colon on the lead-in, uppercase start, a period only on full-sentence items, no mixed instructions and facts, no nesting. | | 4.4 | Use connecting words between sentences on related topics ("Then", "As a result"). | | 4.5 | Put an article (the, a, an) or a demonstrative adjective (this, these) before nouns where applicable. Exception: no article before a noun when an identifier follows it: "Restart pod web-7f9b2". |

Rule 4.2 is the anti-terseness rule. Plain English is short sentences with complete grammar, not telegraph style:

**Wrong shortening:** Ensure file exists before running. **Plain:** Make sure that the file exists before you run the command.

### Section 5 — Procedural writing (Rules 5.1-5.5)

| Rule | Instruction | |---|---| | 5.1 | Maximum 20 words per sentence. Warnings and cautions included. | | 5.2 | One instruction per sentence, unless two actions happen at the same time. A step can add one sentence for an immediate result or limit. | | 5.3 | Write instructions in the imperative: "Run the migration." | | 5.4 | Put a required condition before the command, divided by a comma: "If the build fails, read the log." | | 5.5 | Notes give information, never instructions or limits. A limit belongs with its action. Notes test: the procedure must still work for a reader who deletes all notes. |

**Before:** You'll want to grab the API key from the dashboard before configuring the client, which you can do under Settings. **After:** Get the API key from the dashboard, under Settings. Then configure the client with this key.

### Section 6 — Descriptive writing (Rules 6.1-6.6)

| Rule | Instruction | |---|---| | 6.1 | Give information gradually: one new fact per sentence. | | 6.2 | Use key words and phrases to give the text a logical structure. | | 6.3 | Maximum 25 words per sentence. | | 6.4 | Group related information in paragraphs. | | 6.5 | One topic per paragraph. | | 6.6 | Maximum six sentences per paragraph. |

No imperative in descriptive text. Descriptions explain. Procedures instruct.

### Section 7 — Safety instructions (Rules 7.1-7.3)

| Rule | Instruction | |---|---| | 7.1 | Use a word that shows the risk level ("WARNING" = injury, "CAUTION" = damage). If the two risks occur together, use "WARNING". | | 7.2 | Start with a clear command or condition. | | 7.3 | Then give the risk or the possible result. |

Never bury the instruction after the explanation. The same pattern fits destructive CLI flags and irreversible migrations.

**Before:** Note that data loss may occur in some circumstances if the destructive flag happens to be enabled when running against production. **After:** CAUTION: Do not use the `--force` flag against production. The flag deletes rows that do not match the source.

### Section 8 — Punctuatio

--- name: simple-english description: | Write or rewrite text in plain, layman-readable English in the spirit of ASD-STE100 Simplified Technical English: short sentences, active voice, simple tenses, one word one meaning, condition before command, every technical term defined at first use, no AI slop. Default mode is Plain. Strict mode applies full STE vocabulary compliance when the user names STE, ASD-STE100, or compliance. Use for documentation, READMEs, runbooks, procedures, error messages, release notes, incident reports, API guides, and explanations for readers outside the field. Also use when the user says "STE", "Simplified Technical English", "ASD-STE100", "plain English", "layman's terms", "explain it simply", "no jargon", "de-slop", "make this readable", "write for non-native readers", or asks for docs that translate well. The same rules govern the reply: answer first, five sentences or fewer. license: MIT compatibility: claude-code cursor codex gemini-cli opencode metadata: version: "2.0.0" standard: ASD-STE100 Issue 9 (2025-01-15) ---

# Simple English: Plain Words, Aerospace Discipline

Write plain English that a smart reader outside your field understands on one read. The rules come from ASD-STE100, the controlled language aerospace uses so a tired mechanic cannot misread an instruction. They also remove the signs of AI writing: long sentences, synonym rotation, hedges, filler. Each sentence must survive one read.

## Your Task

When asked to write or rewrite text:

1. **Select the mode** (Plain or Strict, the table that follows). In Strict mode, read `references/strict-vocabulary.md` before you draft. 2. **Classify each passage** as procedural or descriptive. Every other rule depends on this. 3. **Fix your vocabulary before you draft.** Use `make sure that` for check/verify/confirm/validate/ensure as verbs, and `configuration` for config/settings/options. Use no other word for these concepts in the whole document. 4. **Define a technical term at its first use** when a reader outside the field needs it: concept words, not product names or the tool the document is about. 5. **Apply the catalog** that follows. For replies and explanations for outsiders, apply the Plain English rules first. 6. **Do the self-check** before you deliver. This step is not optional. 7. **Never touch code**, identifiers, commands, or quoted errors (see Untouchables).

When asked to CHECK text instead of writing it, report each violation as: rule number, the offending text, a compliant rewrite. Cite only rule numbers that exist in this file, never from memory: invented rule numbers are a known failure.

## Two Modes

| Mode | When | What you apply | |---|---|---| | **Plain** (default) | The user wants clear text: docs, READMEs, error messages, answers | Every structural rule in the catalog. Domain words stay ("idempotent", "webhook"). Replies and explanations for outsiders also get the Plain English rules. | | **Strict** | The user names STE, ASD-STE100, or compliance | Plain mode plus the dictionary discipline in `references/strict-vocabulary.md`. Document only: the reply to the user stays Plain. |

## Step 1: Classify the Text

| | Procedural (instructions) | Descriptive (explanations) | |---|---|---| | Purpose | Tell the reader what to do | Explain what a thing is or does | | Verb form | Imperative: "Install the pump." | Simple present/past/future | | Sentence limit | **20 words** (Rule 5.1) | **25 words** (Rule 6.3) | | Unit rule | One instruction per sentence (5.2) | One topic per paragraph (6.5), max six sentences per paragraph (6.6) |

Do not mix the two in one passage. A "Getting started" section is procedural: headed, numbered where steps follow each other, imperative. An "Architecture" section is descriptive.

## Plain English for Readers Outside the Field

Apply these six rules to your reply to the user and to explanations written for readers outside the field. Procedures and reference documents follow the catalog alone: the catalog measured best there, and these rules dilute it.

1. **Common word over jargon.** When a plain word exists, use it: "use" not "utilize", "start" not "initiate", "help" not "facilitate". `references/word-swaps.md` has the map. 2. **Define a technical term at its first use when the reader needs it.** The reader is smart and outside your field, but the document sets what they already know: do not define the tool the document is about, product names, or standard names (Postgres, S3, HTTP, JSON). Define the concept words: "idempotent (safe to run twice)", "a webhook (an HTTP call sent when an event occurs)". Keep a definition under ten words, at most one per sentence. If it pushes the sentence over the limit, give the definition its own sentence. Never use a synonym of a chosen term inside a definition (Rule 1.11). 3. **Address the reader as "you" and name the actor.** Every sentence says who does what (Rule 3.6): "You run the migration. The database rebuilds the table." 4. **Lead with the point.** The first sentence of a section, and of a reply, states the result or what the reader must do. Explanation follows. 5. **One idea per sentence, one topic per paragraph** (Rules 5.2, 6.1, 6.5). 6. **Say what is true, not how important it is.** "The cache expires after 60 seconds", not "It is crucial to note that the cache expires".

**Before:** To facilitate onboarding, it is crucial that users initiate the idempotent sync prior to configuration. **After:** Before you configure the client, start the sync. The sync is idempotent (you can run it again without side effects).

## THE RULE CATALOG

53 rules in 9 sections, paraphrased from ASD-STE100 Issue 9 with software examples. Rules marked (S) are Strict mode only (see `references/strict-vocabulary.md`). The official wording is in the free standard at asd-ste100.org.

### Section 1 — Words (Rules 1.1-1.14)

| Rule | Instruction | |---|---| | 1.1-1.4, 1.6 (S) | Use only approved words, as their listed part of speech, meaning, and form. | | 1.5 | You can use domain words as technical nouns ("webhook", "commit", "endpoint"). | | 1.7 | Do not use technical nouns as verbs. | | 1.8 | Use the technical nouns of your project or industry. | | 1.9 | When you pick a technical noun, pick a short and clear one. | | 1.10 | No regional, slang, or jargon words as technical nouns. | | 1.11 | One item, one name. Do not call it "config" here and "settings" there. | | 1.12 | You can use domain verbs as technical verbs ("deploy", "compile", "merge"). The standard names computer verbs as legal: click, type, copy, paste, delete, save, install, download, update, and more. When a common verb does the same job, prefer it: "find" instead of "detect". | | 1.13 | Do not use technical verbs as nouns. | | 1.14 | Use American English spelling. |

In Plain mode, rules 1.5, 1.8, and 1.12 make your domain vocabulary legal. The ones agents break are 1.7, 1.11, and 1.13.

**Before:** You can webhook the event, then do a deploy. **After:** Send the event to the webhook. Then deploy the service.

### Section 2 — Multi-word nouns (Rules 2.1-2.2)

| Rule | Instruction | |---|---| | 2.1 | Write multi-word nouns of three words or fewer. | | 2.2 | When a technical noun needs more than three words, write it in full once, then give a short form or hyphenate the units. |

Break long noun chains with prepositions (of, on, in, for):

**Before:** the connection pool timeout configuration value **After:** the timeout value for the connection pool

### Section 3 — Verbs (Rules 3.1-3.7)

| Rule | Instruction | |---|---| | 3.1 (S) | Use only the verb forms that the dictionary gives. | | 3.2 | Use only: infinitive, imperative, simple present, simple past, simple future, past participle as adjective. | | 3.3 | Use the past participle only as an adjective ("the cached response"). | | 3.4 | No auxiliary verbs for complex constructions. No present perfect, no "is to be installed". | | 3.5 | Use an "-ing" form only as a technical noun or inside one ("logging", "the mounting bracket"), never as a verb. | | 3.6 | Active voice. In descriptive text, passive is legal only when the agent is unknown. To repair an agentless passive, use "you" (the reader) or "we" (your company): "Indexes are not used on this table" → "We do not use indexes on this table." | | 3.7 | Describe an action with a verb, not a noun ("compress the file", not "perform compression of the file"). |

**Approved modals: can, will, must. Banned: should, would, may, might, could.** The standard rejects "could" even for possibility: write "an explosion can occur", never "could occur". For "should": a requirement becomes "must". A suggestion is stated as fact or deleted. This matters double for agent instructions, because models read "should" as optional.

**Before:** The migration has completed and the table is being rebuilt. **After:** The migration completed. The database rebuilds the table.

### Section 4 — Sentences (Rules 4.1-4.5)

| Rule | Instruction | |---|---| | 4.1 | Write short and clear sentences. | | 4.2 | Do not omit words or use contractions to shorten sentences. Keep articles, keep "that". | | 4.3 | Use a vertical list for complex text: colon on the lead-in, uppercase start, a period only on full-sentence items, no mixed instructions and facts, no nesting. | | 4.4 | Use connecting words between sentences on related topics ("Then", "As a result"). | | 4.5 | Put an article (the, a, an) or a demonstrative adjective (this, these) before nouns where applicable. Exception: no article before a noun when an identifier follows it: "Restart pod web-7f9b2". |

Rule 4.2 is the anti-terseness rule. Plain English is short sentences with complete grammar, not telegraph style:

**Wrong shortening:** Ensure file exists before running. **Plain:** Make sure that the file exists before you run the command.

### Section 5 — Procedural writing (Rules 5.1-5.5)

| Rule | Instruction | |---|---| | 5.1 | Maximum 20 words per sentence. Warnings and cautions included. | | 5.2 | One instruction per sentence, unless two actions happen at the same time. A step can add one sentence for an immediate result or limit. | | 5.3 | Write instructions in the imperative: "Run the migration." | | 5.4 | Put a required condition before the command, divided by a comma: "If the build fails, read the log." | | 5.5 | Notes give information, never instructions or limits. A limit belongs with its action. Notes test: the procedure must still work for a reader who deletes all notes. |

**Before:** You'll want to grab the API key from the dashboard before configuring the client, which you can do under Settings. **After:** Get the API key from the dashboard, under Settings. Then configure the client with this key.

### Section 6 — Descriptive writing (Rules 6.1-6.6)

| Rule | Instruction | |---|---| | 6.1 | Give information gradually: one new fact per sentence. | | 6.2 | Use key words and phrases to give the text a logical structure. | | 6.3 | Maximum 25 words per sentence. | | 6.4 | Group related information in paragraphs. | | 6.5 | One topic per paragraph. | | 6.6 | Maximum six sentences per paragraph. |

No imperative in descriptive text. Descriptions explain. Procedures instruct.

### Section 7 — Safety instructions (Rules 7.1-7.3)

| Rule | Instruction | |---|---| | 7.1 | Use a word that shows the risk level ("WARNING" = injury, "CAUTION" = damage). If the two risks occur together, use "WARNING". | | 7.2 | Start with a clear command or condition. | | 7.3 | Then give the risk or the possible result. |

Never bury the instruction after the explanation. The same pattern fits destructive CLI flags and irreversible migrations.

**Before:** Note that data loss may occur in some circumstances if the destructive flag happens to be enabled when running against production. **After:** CAUTION: Do not use the `--force` flag against production. The flag deletes rows that do not match the source.

### Section 8 — Punctuatio