Asd Ste100
Use when English text must be parsed without a human to resolve ambiguity — tool descriptions, error messages, inter-agent instructions, system prompts, status reports — and misreading has a real cost, or when text reads as dense, hedged, or easy to misparse. Triggers: disambiguate, STE100 rewrite, apply Simplified Technical English, plain-language rewrite, controlled-language rewrite, rewrite so an agent cannot misread this. Not for creative or marketing copy.
- Skill ID
- danyuchn/asd-ste100-skill/asd-ste100
- Publisher
- danyuchn
- Repository
- asd-ste100-skill
- Installs
- 264
- Files
- 7
- Synced
- Oct 7, 2026
Open any RiverX project, open the Skills panel in the chat, and search for this identifier. The files are fetched from the source repository at install time.
danyuchn/asd-ste100-skill/asd-ste100Installs these files- LICENSE
- README.md
- SKILL.md
- examples/before-after.md
- examples/linter-edge-cases.md
- references/writing-rules.md
- scripts/ste-lint.py
What this skill tells the agent
Simplified Technical English (ASD-STE100)
ASD-STE100 is a controlled-language standard built by the aerospace and defense industry (ASD, the AeroSpace and Defense Industries Association of Europe) to stop maintenance technicians from misreading English instructions. The standard removes the two biggest sources of misreading: words with more than one meaning, and sentences with more than one possible structure.
This skill borrows that same discipline for a different reader: an AI agent or a downstream system that has to parse an English string — an error message, a tool description, an inter-agent instruction, a status report — without a human in the loop to resolve ambiguity. If a maintenance technician can misread "close the valve" as an adjective ("the valve that is near") instead of a command, so can a language model.
When to Use This Skill
- An agent's output (explanation, instruction, log message, tool description) reads as dense, jargon-heavy, or ambiguous.
- Text will be consumed by another agent, a translation pipeline, or a non-native English reader, and misparsing has a real cost.
- You are writing a prompt, system message, or tool description and want to remove ambiguity before a model ever sees it.
- You want a before/after comparison showing exactly which rule was violated and how the rewrite fixes it. Ask for it — the default output is the rewritten text alone (see Output Format).
This skill is not for creative or marketing copy — STE is deliberately flat and literal. Do not apply it to text where voice, nuance, or persuasion is the point.
Two Modes
Pick a mode before rewriting. If the user does not say which, infer from the text type and state the choice in one line.
Strict — procedures, error messages, tool and function descriptions, inter-agent instructions, safety text. Anywhere a wrong reading has a cost. Apply every rule below, including the hard length caps and one-word-one-meaning discipline.
STE-flavored — READMEs, PR descriptions, changelogs, explanatory prose. Apply the structural rules in full and treat the lexical rules as advisory (see Core Rewrite Rules for that split). In practice that means keeping the sentence length caps, active voice, simple tenses, no phrasal verbs, no semicolons, no nominalization and no marketing adjectives, while dropping the one-word-one-meaning lockdown: prose needs some range, and a strict rewrite of prose reads as a personality transplant rather than a clarification.
The two modes and the structural/lexical split are the same distinction seen from two directions. The split says which rules this skill can verify without ASD's dictionary. The modes say which of them to enforce for a given kind of text.
Source and Scope
This skill encodes the rule categories of ASD-STE100 Issue 9 (Jan 2025): 53 writing rules across 9 sections covering word choice, grammar, sentence structure, and style, backed by a dictionary of ~900 approved words (one meaning, one part of speech each) and ~1,200 words to avoid with suggested replacements. See references/writing-rules.md for the full rule summary and citations.
It does not reproduce ASD's ~900-word approved dictionary verbatim. ASD-STE100 is free to obtain, but it is not free to redistribute: Issue 9, page 2 states that "no reproduction or publication of it, in whole or in part, shall be made without the written authority of an officer of ASD," and grants free reproduction rights only to eight listed categories (ASD/AIA/AIAC member associations and their member companies and customers, member-state defence ministries, A4A, airworthiness authorities, and universities and research institutes for educational purposes). This project is in none of them, so the dictionary stays out of this repo.
Instead, this skill applies the underlying principle (pick the plainest, most common word available and use it the same way every time) rather than checking against a fixed word list. When exact ASD-approved wording matters (e.g. actual aircraft maintenance documentation), get the standard and check word-by-word against the real dictionary. Request it from the official downloads page — note that this is a request form that emails you a link, not a direct download.
Core Rewrite Rules
STE's rules divide into two kinds, and this skill can only fully deliver one of them. Structural rules are self-contained: they describe sentence shape, and you can apply them from the description alone. Lexical rules are defined entirely by the official ~900-word dictionary, which this skill deliberately does not reproduce (see Source and Scope). Without that dictionary, the lexical rules degrade from a checkable standard into a preference for plain words.
Apply the structural rules with confidence. Apply the lexical rules as a direction of travel, and say so in your output rather than implying dictionary compliance you cannot verify.
Structural rules — apply these
| Rule | Do | Don't |
|---|---|---|
| Active voice | "The agent deletes the file." | "The file is deleted (by the agent)." — unless the actor is genuinely unknown or irrelevant |
| No phrasal verbs (Rule 9.3) | "Remove the panel." / "Start the job." | "Take off the panel." / "Spin up the job." — a two-word verb has meanings the parts do not predict |
| One instruction per sentence | "Open the file. Read line 3." | "Open the file and read line 3, then check if it matches." |
| Sentence length | ≤20 words for instructions/procedures, ≤25 words for descriptions | Long compound/subordinate-clause sentences |
| No semicolons (Rule 8.1) | Split into separate sentences | Any semicolon at all — STE bans the mark outright, not only as a clause join. (Rule 8.1 permits every other standard punctuation mark. The em dash is not banned by STE, though it often signals a sentence that should be split.) |
| Noun clusters | ≤3 words stacked as a noun phrase ("fuel pump valve") | 4+ word noun stacks ("high pressure fuel pump inlet valve assembly") |
| No ellipsis | Keep the subject, verb, and article explicit even if it reads longer | Drop words to save space ("Files not backed up will be lost" → ambiguous which files) |
| Keep modality | "The request may have failed." stays "may have" | Promote a hedge to a fact ("The request failed.") or invent a certainty the source did not state |
| Paragraph limits | One topic per paragraph, ≤6 sentences | Multi-topic paragraphs |
| Lists for sequences | Use a numbered or bulleted list for 3+ steps or conditions | Bury a sequence inside one prose sentence |
Lexical rules — direction of travel only
| Rule | Do | Don't | Why it is weaker here |
|---|---|---|---|
| One word, one meaning | Pick one verb for one action and reuse it every time (e.g. always "check", never mix "check"/"verify"/"confirm" for the same action) | Rotate synonyms for the same idea across a document | Consistency within a document is checkable. Which word is the approved one is not, without the dictionary. |
| One part of speech per word | "Apply oil to the valve" (oil = noun) | "Oil the valve" (oil = verb) | Whether "oil" is approved as a noun only is a dictionary fact. Prefer the noun form when both read equally well. Do not claim compliance. |
| Verb, not noun (Rule 3.7) | "Analyze the log." | "Perform an analysis of the log." — a noun form of an action makes the sentence longer and hides who acts | Rule 3.7 says "use an approved verb to describe an action." Preferring the verb form is safe to apply anywhere. Knowing which verb is the approved one needs the dictionary. |
| Domain terms | Keep necessary technical nouns/verbs, but define them once if not common English (STE allows a project-specific glossary beyond its base dictionary) | Use jargon without ever defining it | The glossary allowance is real STE, but the base dictionary it extends is absent. |
Simple tenses — apply with one exception
Use this skill in a project
Open any RiverX project, search the Skills panel for danyuchn/asd-ste100-skill/asd-ste100, and install it in one click.