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.

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.

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 — that document is ASD's own free-to-download standard, not something to copy wholesale. 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), download the official standard at https://www.asd-ste100.org/ and check word-by-word against the real dictionary.

Core Rewrite Rules

Rule	Do	Don't
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
One part of speech per word	"Apply oil to the valve" (oil = noun)	"Oil the valve" (oil = verb) — if "oil" is only approved as a noun
Active voice	"The agent deletes the file."	"The file is deleted (by the agent)." — unless the actor is genuinely unknown or irrelevant
Simple tenses only	"We received the report." (simple past)	"We have received the report." (present perfect)
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
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)
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
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

Process

1. Read the input text once for meaning — do not start rewriting before you understand what it must still say afterward.
2. Walk it sentence by sentence and flag every rule violation (word ambiguity, tense, voice, length, ellipsis, noun stacking).
3. Rewrite each flagged sentence to fix the violation while preserving the original meaning exactly. If a rewrite would drop necessary precision (a safety condition, a scope qualifier, a number), keep the longer phrasing and flag it instead of silently simplifying.
4. Produce a before/after table (see Output Format).
5. If the input already complies, say so — do not force changes onto compliant text.

Output Format

| Rule violated | Original | Simplified |
|---|---|---|
| Present perfect tense | "We have received your request." | "We received your request." |
| Noun cluster (4+ words) | "the agent task queue priority handler" | "the handler that sets task-queue priority" |

Follow the table with a one-line note on anything you deliberately did not simplify, and why (usually: simplifying would lose required precision).

Boundaries

Will:

• Rewrite ambiguous or dense English into short, single-meaning, active-voice sentences.
• Flag exactly which rule a sentence violates before rewriting it.
• Preserve every fact, condition, and scope qualifier in the original.
• Suggest a one-line glossary entry for domain terms that must stay.

Will not:

• Reproduce ASD's official ~900-word dictionary as if it were memorized verbatim — always treat the official download as the source of truth for exact approved wording.
• Simplify creative, marketing, or persuasive copy where voice and nuance are the point.
• Silently drop a safety condition, exception, or scope qualifier to shorten a sentence — it will flag the trade-off instead.
• Guarantee an aerospace/defense-grade STE-compliant document; this is a general-purpose clarity tool inspired by STE, not a certified STE authoring tool.

Additional Resources

• references/writing-rules.md — fuller summary of the 9 rule sections and dictionary structure, with citations to the official standard and secondary sources.
• examples/before-after.md — worked examples, including official STE examples and agent-output examples built for this skill.