version: "1.0.1" name: write-device-skill description: >- Use when authoring a DEVICE-SKILL.md for a new Resident-based firmware project. Walks the user through hardware, Lua module surface, examples, and constraints. Triggered when the user says "write a device skill", "set up DEVICE-SKILL.md", or invokes /resident:write-device-skill.

write-device-skill

Help the user produce a DEVICE-SKILL.md for a Resident-based firmware project. The output is a single Markdown file at the firmware project root that documents the device-specific Lua surface — hardware, modules, examples, constraints. Sandbox-generic content (lifecycle callbacks, ctx, log, time, store, events) is NOT in DEVICE-SKILL.md; it lives in Resident's own docs and is loaded by the create-app skill.

Audience

DEVICE-SKILL.md is written for Lua app authors targeting the device sandbox. The reader is someone composing a Lua app and pushing it to a running device — they do not have the firmware source open and cannot change it. Frame everything from that perspective: the runtime contract (what modules and variables exist, what they do, what ranges are valid). Do NOT describe the C++ firmware layer — no SandboxConfig fields, no driver registration, no "to enable X the firmware would need to..." asides. If a capability isn't exposed to Lua, just say so plainly and move on.

What you need

1. Firmware project root — defaults to cwd. Ask if not in one.
2. Device identity — short name (e.g. "M5StickC Plus2", "<My Hardware Startup> lamp").
3. Driver surface — which Resident::Driver / Resident::Extension

subclasses the firmware registers, and what each one's name() and Lua module functions are.

Workflow

1. Read the template at

${CLAUDE_PLUGIN_ROOT}/skills/write-device-skill/tools/template.md. ${CLAUDE_PLUGIN_ROOT} is set by Claude Code to the absolute path of the installed plugin — always use it to reference bundled files; the CWD is the user's project, not the skill directory.

1. Read the reference example at

${CLAUDE_PLUGIN_ROOT}/skills/write-device-skill/tools/example.md — that's the seeded M5StickC Plus2 DEVICE-SKILL.md, useful as a quality bar.

1. Ask the user (one question at a time):

• Device name + a one-paragraph overview.
• Hardware list (screen? sensors? audio? buttons? indicators?).

For each, ask for size/units/coordinate frames.

• Driver modules: which Lua module names are exposed (e.g. screen,

imu)? For each, ask the user to walk through the available functions, signatures, and any defaults/ranges.

• 3–6 example apps that exercise the modules. The agent can draft

these from the hardware description; user confirms.

• Constraints (dimensions, ranges, memory).
• Optional: device-specific practical tips.
• Optional: a ## Validation stubs Lua block (see template.md and

example.md for format). This makes validate-app produce realistic getter return values instead of nil, so apps that compute against screen.width() etc. validate cleanly. Skip if the device has no numeric or multi-value getters.

1. Write the result to <project-root>/DEVICE-SKILL.md. Do NOT include

sandbox-generic content (lifecycle, ctx, log/time/store/events).

1. Show the user a diff/summary and confirm before writing.

Pointers when interviewing

• A driver's Lua module name is whatever its Extension::name() returns

in C++. If the user has firmware source open, point them at the Driver subclass declarations.

• Module function signatures come from LuaModule::method<> /

staticMethod / constant calls in registerModule().

• For sensors that return multiple values (e.g. imu.accel() returning

ax, ay, az), Lua-style multi-return is the convention.

• Coordinate frames matter — document body frame, screen orientation,

and the sign conventions of any axis.

What NOT to put in DEVICE-SKILL.md

These are sandbox-generic and live in Resident's own docs (loaded by create-app). DON'T duplicate them per device:

• App lifecycle: init(ctx), on_tick(ctx, dt_ms), on_event(ctx, event)
• The ctx table fields (time_ms, generation_id)
• Built-in modules: log.*, time.*, store.*, events.*, surfaces.*
• Lua's own libraries (math.*, string.*, table.*)

If the firmware exposes a device-specific module that overlaps with one of these names, document it under Lua Modules — but don't restate the universal modules.