Agent skill

The MCP server gives an agent hands. @extension.dev/skill gives it judgment: when to reach for which tool, the cross browser rules, the silent failure gotchas, and the publish checklist. The package ships one agent skill in the open Agent Skills format: plain markdown, no login, no network, so it works with any agent that reads the format.

Install

Through the plugin marketplace:

/plugin marketplace add extensiondev/skill
/plugin install extension-dev@extensiondev

Or from npm, version locked to your dependency tree:

npm i -D @extension.dev/skill

Skills-aware installers link the npm copy into your agents automatically on install. The manual fallback is a copy:

cp -R node_modules/@extension.dev/skill/skills/extension-dev .claude/skills/

What is inside

One 6-step workflow: start from a template, treat the manifest as the source of truth, write cross browser by default, develop with feedback rather than faith, build and verify per browser, publish deliberately.

Reference files back the steps. All seven:

File	Covers
api-gotchas.md	Service worker, permissions, tabs, messaging and runtime API traps
cross-browser.md	Firefox differences, manifest prefixes, namespace choices
debugging.md	Reading the live browser instead of guessing
project-structure.md	File layout, HTML mount patterns, config
publishing.md	Zips, store accounts, listings, the order that passes review
store-md.md	Store metadata and reviewer notes in STORE.md
templates.md	Choosing a starting point from the catalog

Why both

Extensions fail quietly. A content script that never injects, a panel that never opens, a permission that returns undefined with no error. An agent with tools but no judgment will call them, read a plausible result, and move on.

Package	Supplies
@extension.dev/mcp	The verbs: scaffold, run, inspect, act, ship
@extension.dev/skill	The rules: what to check, in what order, and when a result is a lie

The skill works on its own, since every capability documents the extension CLI path. It does more with the MCP server connected, because it tells the agent to verify against the live browser rather than guess, and the tools make that one call.

When it fails

• The skill never triggers: confirm it landed in .claude/skills/extension-dev or your agent's skills directory. Agents without skills support need one line in AGENTS.md pointing at the skill's SKILL.md.
• npm i linked nothing: your installer is not skills aware. Use the manual copy above.

Next

• MCP server for the tools it directs
• CLI for the command line path it documents