What it does. Write technical documentation in Simplified Technical English (ADS-STE100). Use when creating, editing, or reviewing maintenance manuals, technical guides, SOPs, or any aerospace/defense/engineering documentation that requires controlled language. From sdsheeks/ste100-skill, listed on Agent skills.

Upstream	sdsheeks/ste100-skill
Skill file	SKILL.md
License	MIT (skill folder LICENSE)
Author	sdsheeks
Fetched	2026-09-10

Install

• npx skills add sdsheeks/ste100-skill --skill ste100, or copy the skill folder into ~/.claude/skills/ste100/.
• Raw file: curl -sL https://raw.githubusercontent.com/sdsheeks/ste100-skill/HEAD/SKILL.md

SKILL.md (verbatim)

name: ste100
description: Write technical documentation in Simplified Technical English (ADS-STE100). Use when creating, editing, or reviewing maintenance manuals, technical guides, SOPs, or any aerospace/defense/engineering documentation that requires controlled language.
metadata:
  author: sdsheeks
  license: MIT
  spec: ASD-STE100 Issue 8

STE100 Skill

Write technical documentation that follows Simplified Technical English (STE), the controlled language defined in ASD-STE100.

STE exists because complex equipment requires clear instructions. Ambiguity in a maintenance manual can ground an aircraft. Ambiguity in a procedure can cause injury. STE eliminates ambiguity by restricting vocabulary, grammar, and sentence structure.

When to Use

Use this skill for:

• Maintenance manuals and service bulletins
• Standard operating procedures (SOPs)
• Technical installation guides
• Airworthiness instructions
• Any documentation where a non-native English speaker must follow steps without misinterpretation

Do not use for marketing copy, blog posts, or internal chat. STE is for documentation where clarity prevents failure.

Writing Rules

Grammar Rules

Rule	Constraint
Sentences	Maximum 20 words
Nouns per sentence	Maximum 6
Verbs per sentence	Maximum 1 (active voice only)
Voice	Active only. No passive constructions
Tense	Present tense for instructions, past tense for descriptions
Articles	Use "the" for specific items, "a/an" for general items. Never omit
Pronouns	Avoid where possible. Use the noun instead
Abbreviations	Define on first use. Use the abbreviation after
Numbers	Spell out 1-10. Use digits for 11+
Hyphenation	Use for compound modifiers before a noun

Vocabulary Rules

STE limits vocabulary to approved words. See references/approved-words.md for the full list.

Key principles:

1. One word, one meaning. "Follow" always means track or trace. "Proceed" means go forward. Never use "follow" to mean "proceed."

2. Use the approved word. If a technical term has an approved STE word, use it. If not, use the simplest possible word.

3. No jargon. Replace domain-specific synonyms with the approved term.

Common substitutions:

Do not use	Use instead
commence	start
utilise / utilize	use
in order to	to
ascertain	find, make sure
facilitate	help, let
prior to	before
subsequent to	after
terminate	stop
initiate	start
component	part
requires	needs, must
indicates	shows
approximately	about
modification	change
demonstrate	show
eliminate	remove
adjacent	next to

Structure Rules

1. One topic per sentence. If you need "and" to connect two actions, split into two sentences.

2. One instruction per step. Each step in a procedure does one thing.

3. Use vertical lists. List items vertically, not inline. Each item is a separate line.

4. Use headings. Break content into short sections. A section covers one topic.

5. No hidden instructions. "Make sure the valve is open" is passive. "Open the valve" is active.

Procedure Format

Technical procedures follow a strict format. See references/procedure-format.md for the full template.

Minimum structure:

• Title — what the procedure accomplishes
• Conditions — when to perform it, prerequisites
• Tools/Parts — what is needed
• Steps — numbered, one action each, imperative mood
• Expected Results — what success looks like

Quick Checks

Before delivering documentation:

• Any sentence over 20 words? Split it.
• Any passive voice? Rewrite in active. "The valve is opened" becomes "Open the valve."
• Any word not on the approved list? Replace it.
• Any sentence with more than one verb? Split it.
• Any noun missing an article? Add "the" or "a/an."
• Any abbreviation not defined on first use? Define it.
• Any procedure step doing two things? Split into two steps.
• Any inline list with 3+ items? Move to vertical format.
• Any technical jargon? Replace with approved word.
• Any "and" connecting two actions? Split into two sentences.

Scoring

Rate each dimension 1-10:

Dimension	Question
Simplicity	Could a non-native speaker follow this?
Clarity	Is each instruction unambiguous?
Completeness	Are all steps and parts listed?
Consistency	Does every term match the approved word list?
Structure	Does each sentence contain one idea?

Below 40/50: revise before publishing.

References

• references/approved-words.md — STE approved vocabulary with meanings
• references/procedure-format.md — procedure template and formatting rules
• references/examples.md — before/after transformations

License

MIT

Other files in this skill

• LICENSE
• README.md
• references/approved-words.md
• references/examples.md
• references/procedure-format.md

README.md (verbatim)

ste100-skill

A skill for writing technical documentation in Simplified Technical English (ADS-STE100). Works with OpenCode, Claude, ChatGPT, and any AI agent that supports custom instructions or skills.

What it does

STE100 is a controlled language specification from the Aerospace and Deflang Association. It restricts English to a simplified vocabulary and grammar rules so technical documentation is clear and unambiguous.

This skill teaches an AI agent to write STE-compliant documentation: maintenance manuals, SOPs, technical guides, and any procedure where ambiguity can cause failure.

What it checks

• Sentence length (max 20 words)
• Active voice only
• One verb per sentence
• Approved vocabulary
• Procedure formatting
• Warning placement
• Article usage
• Abbreviation definitions

Install

OpenCode

Copy the ste100 folder to one of these locations:

~/.agents/skills/ste100/
~/.config/opencode/skills/ste100/
.opencode/skills/ste100/

Or clone directly:

git clone https://github.com/sdsheeks/ste100-skill.git ~/.agents/skills/ste100

Restart OpenCode after installing. The skill loads automatically when you ask for technical documentation.

Claude (claude.ai or Claude Desktop)

1. Start a new conversation
2. Click the + icon in the message bar
3. Select Add from files or drag the files in
4. Upload these files from the skill:
   • SKILL.md
   • references/approved-words.md
   • references/procedure-format.md
   • references/examples.md
5. Start your prompt with: "Follow the STE100 skill instructions to write..."

Claude uses uploaded files as project knowledge. The files stay in the conversation until you remove them.

Claude Code

Copy the skill to the Claude skills directory:

git clone https://github.com/sdsheeks/ste100-skill.git ~/.claude/skills/ste100

Restart Claude Code. The skill loads automatically when relevant.

ChatGPT

Option 1: Custom Instructions

1. Go to Settings > Personalization > Custom Instructions
2. Paste this into the "What would you like ChatGPT to know?" box:

When I ask you to write technical documentation, follow these STE rules:
- Maximum 20 words per sentence
- Active voice only, no passive constructions
- One verb per sentence
- Use approved STE vocabulary (use instead of utilize, start instead of commence, etc.)
- One instruction per step in procedures
- Every noun needs an article (the, a, an)
- Define abbreviations on first use
- Spell out numbers 1-10, use digits for 11+
- Place warnings before the step they apply to
- Use vertical lists, not inline lists

Approved word substitutions:
- utilize → use
- commence → start
- terminate → stop
- facilitate → help
- ascertain → find
- prior to → before
- subsequent to → after
- component → part
- demonstrate → show
- eliminate → remove
- adjacent → next to
- approximately → about
- modification → change

3. Click Save

Option 2: Upload Files

1. Start a new conversation
2. Click the + icon and select Upload from computer
3. Upload SKILL.md, references/approved-words.md, references/procedure-format.md, and references/examples.md
4. Ask ChatGPT to write technical documentation

Option 3: Project Knowledge (Plus/Team/Enterprise)

1. Go to Projects in the sidebar
2. Create a new project or open an existing one
3. Click Add files under Project Knowledge
4. Upload the skill files
5. Start a conversation in that project. ChatGPT references the uploaded files automatically.

Cursor / Windsurf / Other AI Code Editors

Copy the skill files into your project:

git clone https://github.com/sdsheeks/ste100-skill.git .cursor/skills/ste100

Or add the rules to your project's .cursorrules file by copying the contents of SKILL.md.

Usage

OpenCode:

@ste100 write a procedure for replacing the fuel filter

Claude:

Follow the STE100 skill instructions to write a procedure for replacing the fuel filter.

ChatGPT:

Write a maintenance procedure for replacing the fuel filter. Use the STE rules from my custom instructions.

References

• references/approved-words.md — STE approved vocabulary with meanings
• references/procedure-format.md — procedure template and formatting rules
• references/examples.md — before/after transformations

License

MIT

references/approved-words.md (verbatim)

STE Approved Words

These words have approved meanings in STE. Use them only in the approved sense.

Verbs

Word	Approved meaning	Do not use for
add	put together, join	increase
apply	put on, spread	use, implement
break	separate into parts	stop
build	make, construct	create
carry	move from one place to another	contain, hold
cause	make happen	allow, let
check	examine, verify	control, inspect
clean	remove dirt	clear
close	move to a stopped position	shut (use close)
connect	join two or more items	attach, couple
consider	think about	believe, feel
contain	have as parts	include
control	operate, regulate	check, verify
cool	make less hot	—
correct	make right	repair, fix
cut	divide with a tool	separate
decrease	make smaller	reduce
deliver	take to a destination	provide, give
do	perform	make, carry out
examine	look at carefully	inspect, check
exchange	give and receive	replace, swap
fit	put in position	install
flush	clean with liquid	wash
fold	bend over	—
get	obtain, receive	acquire, obtain
go	move to	travel, proceed
heat	make hotter	—
hold	keep in position	maintain, support
include	have as parts	contain
install	put in position for use	fit, mount
keep	continue to have	maintain, retain
let	allow	make, cause
lift	move up	raise
lock	secure with a lock	fasten, secure
make	produce, create	build, form
mark	put a sign on	label, indicate
measure	find the size of	test, check
move	change position	shift, transfer
open	move to an opened position	—
operate	use, control	control, run
perform	carry out	do, execute
permit	allow	let, cause
place	put in a position	put, set
protect	keep safe from damage	guard, defend
remove	take away	eliminate, extract
repair	restore to working order	fix, correct
replace	put back in position	substitute
rotate	turn around	turn
run	operate	operate, use
seal	close tightly	close, lock
select	choose	pick
separate	move apart	disconnect, divide
set	put in a particular position	place, put
show	make visible	indicate, demonstrate
stop	cease operation	halt, terminate
test	check performance	verify, examine
tighten	make tighter	secure, fasten
transfer	move from one place to another	carry, shift
turn	move around a point	rotate
turn off	stop operation	stop, shut down
turn on	start operation	start, activate
use	employ for a purpose	utilize, apply
verify	make sure	confirm, check
wash	clean with liquid	clean, flush
write	put words on a surface	enter, record

Nouns

Word	Approved meaning	Do not use for
assembly	group of parts	component, unit
bolt	threaded fastener with a head	screw (use bolt if it has a head)
builder	person who builds	manufacturer, fabricator
condition	state	status, situation
damage	harm	injury (for things), impairment
document	written information	file, record
drawing	picture with dimensions	diagram, sketch
equipment	tools, machines	apparatus, device
failure	stop of function	fault, malfunction
fastener	device to hold parts	connector, fitting
fit	state of being in position	tolerance (use fit for clearance)
fluid	liquid or gas	liquid (use fluid for both)
gasket	sealing material	seal (use gasket for flat seals)
hand tool	tool operated by hand	—
instruction	direction for action	procedure (use instruction for a single step)
lubricant	substance for lubrication	oil, grease (use lubricant for all)
maintenance	keeping in good condition	service
man	adult male person	person, personnel (use person)
manufacturer	person/company that makes	builder, maker
material	substance	substance, matter
mechanic	person who repairs	technician
nut	threaded fastener without a head	—
operator	person who operates	user, worker
part	single piece of an assembly	component, piece
person	individual	individual, human
procedure	series of steps to do a task	instruction, process
protective equipment	equipment for protection	PPE (spell out)
repair	act of restoring	fix, remedy
service	act of maintaining	maintenance (use maintenance)
washer	flat ring for load distribution	—

Adjectives

Word	Approved meaning	Do not use for
broken	separated into parts	damaged (use broken for separation)
closed	in a stopped position	shut
dangerous	with risk of injury	hazardous, risky
dry	not wet	—
hot	high temperature	warm
open	in an opened position	—
wet	covered with liquid	—

Adverbs

Word	Approved meaning
along	in the direction of
away	from a place
down	toward a lower level
forward	toward the front
inward	toward the inside
outward	toward the outside
up	toward a higher level

Prepositions

Word	Approved meaning
at	specific point in time or space
by	near, next to
for	purpose
from	starting point
in	inside, contained by
of	belonging to, made of
on	in contact with a surface
to	direction, destination
with	together, using

references/examples.md (verbatim)

STE Examples

Before and after transformations showing common STE improvements.

Sentence Length

Before (28 words):

The technician must make sure that all of the fasteners that hold the access panel in place are properly torqued to the specifications that are listed in the maintenance manual before the aircraft can be released for service.

After (14 words):

Check that the access panel bolts are torqued to the values in the maintenance manual.

Split the long sentence. Remove "make sure that all of the fasteners that hold." Use direct language.

---

Passive Voice

Before:

The oil filter is removed by the mechanic.

After:

The mechanic removes the oil filter.

Find the actor. Put them at the front of the sentence.

---

Jargon

Before:

The component should be utilised in accordance with the manufacturer's guidelines.

After:

Use the part as the manufacturer says.

Replace "utilised" with "use." Replace "component" with "part." Replace "in accordance with" with "as." Replace "guidelines" with "says."

---

Multiple Verbs

Before:

Disconnect the battery, remove the four bolts, and take off the panel.

After (three steps):

1. Disconnect the battery.
2. Remove the four bolts.
3. Take off the panel.

One action per step. Split compound instructions.

---

Hidden Instructions

Before:

The valve should be opened to allow the fluid to drain.

After:

Open the valve to let the fluid drain.

Remove "should be." Use imperative mood for instructions.

---

Missing Articles

Before:

Remove bolts from panel.

After:

Remove the bolts from the panel.

Every noun needs an article. Use "the" for specific items, "a/an" for general.

---

Abbreviations

Before:

Check the ECU for fault codes. The ECU controls engine timing.

After:

Check the engine control unit (ECU) for fault codes. The ECU controls engine timing.

Define the abbreviation on first use. Use the abbreviation after.

---

Numbers

Before:

Install three bolts and two washers.

After:

Install 3 bolts and 2 washers.

Use digits for numbers 11 and above. Use words for 1 through 10.

Correction: STE says spell out 1-10. So:

Install three bolts and two washers.

This is correct. The rule is: spell out 1-10, use digits for 11+.

---

Inline Lists

Before:

You will need a wrench, sockets, screwdrivers, and pliers.

After:

You will need:

• A wrench
• Sockets
• Screwdrivers
• Pliers

Move inline lists to vertical format for readability.

---

Warning Placement

Before:

WARNING: Wear safety gloves.

1. Start the procedure.
2. Remove the cover.
3. Check the filter.

After:

1. Start the procedure.
2. Remove the cover.

WARNING: Wear safety gloves. Hot oil can cause burns.

3. Check the filter.

Place warnings directly before the step they apply to, not at the start of the procedure.

---

Sentence Over 20 Words

Before:

Before you begin this procedure, make sure that the engine has been shut down for at least thirty minutes so that all moving parts have stopped and all pressures have equalized.

After:

Make sure the engine is cool. Wait 30 minutes after shutdown.

Split into two sentences. Remove the long dependent clause. Use specific time.

---

Inconsistent Terms

Before:

The bolt is loose. Tighten the screw. Check the fastener.

After:

The bolt is loose. Tighten the bolt. Check the bolt.

Use one word for one thing. If it is a bolt, call it a bolt every time.

references/procedure-format.md (verbatim)

STE Procedure Format

Procedures follow a strict structure. Every procedure uses this format.

Required Sections

1. Title

State what the procedure accomplishes. Use noun phrases, not sentences.

Correct:  Main Engine Oil Change
Incorrect: How to Change the Oil in the Main Engine

2. Conditions

State when to perform the procedure. Include prerequisites and safety conditions.

Conditions:
  The engine is cool.
  The aircraft is on level ground.
  You have the required tools and parts.

Use present tense. Use active voice. One condition per line.

3. Tools and Parts

List every tool and part needed. Use a vertical list.

Tools:
  Torque wrench
  Oil drain pan
  Safety glasses

Parts:
  Oil filter (P/N 123-456)
  Gasket kit (P/N 789-012)
  MIL-PRF-23699 oil (4 quarts)

Use part numbers. Specify quantities. Use approved lubricant names.

4. Safety Warnings

Place warnings before the step they apply to. Do not place warnings at the start of the procedure.

WARNING: Wear safety glasses. Hot oil can cause burns.

1.  Open the drain valve.

Use these signal words only:

• DANGER — immediate hazard, will cause injury or death
• WARNING — potential hazard, could cause injury
• CAUTION — potential hazard, could cause equipment damage

5. Steps

Each step is one action. Use imperative mood. Start with a verb.

1.  Remove the four bolts that hold the access panel.
2.  Take off the access panel.
3.  Put the drain pan under the oil filter.

Rules for steps:

• One action per step. If "and" connects two actions, split into two steps.
• Use the approved word for each verb.
• Maximum 20 words per step.
• Maximum 6 nouns per step.
• Maximum 1 verb per step.
• Use "the" or "a/an" before every noun.
• Do not use passive voice. "The bolts are removed" is wrong. "Remove the bolts" is correct.

6. Expected Results

After a group of steps, state what the result looks like.

When the procedure is complete:
  The new oil filter is installed.
  The drain valve is closed.
  No oil leaks are visible.

Use present tense. State observable conditions.

Formatting Rules

• Use numbered lists for sequential steps.
• Use bullet lists for non-sequential items (tools, parts, conditions).
• Do not mix numbered and bullet lists for the same section.
• Leave a blank line between sections.
• Use short headings. One or two words.
• Do not use bold, italic, or underline in procedural text (use signal words for warnings only).

Example Procedure

TITLE: Main Engine Oil Filter Replacement

CONDITIONS:
  The engine is cool.
  The aircraft is on level ground.

TOOLS:
  Torque wrench (50-250 ft-lb)
  Oil filter wrench
  Safety glasses
  Nitrile gloves

PARTS:
  Oil filter (P/N 123-456)
  Gasket (P/N 123-457)

PROCEDURE:

WARNING: Wear safety glasses and nitrile gloves. Used oil contains harmful chemicals.

1.  Remove the four bolts that hold the filter access panel.
2.  Take off the access panel.
3.  Put the oil filter wrench on the old filter.
4.  Turn the wrench counterclockwise to remove the filter.
5.  Let the oil drain into the pan for 5 minutes.
6.  Clean the filter mounting surface with a lint-free cloth.
7.  Put the new gasket on the new filter.
8.  Screw the new filter on by hand.
9.  Tighten the filter to 25 ft-lb with the torque wrench.
10. Put the access panel back.
11. Install the four bolts. Tighten to 15 in-lb.

EXPECTED RESULT:
  The new filter is installed. No oil leaks are visible. The access panel is secure.

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