cc-chrome-extension: Skill for Claude Code

A tool only works when all four pieces exist. Do them in this order and stop at the first mismatch.

1. Extension handler — extension/background.js

Add a key to the handlers object. The key is the wire method name.

async my_tool(params) {
  const tab = await resolveTab(params);        // honors params.tabId, falls back to active tab
  return await execInTab(tab, pageMyTool, [params.someArg ?? default]);
}

• Anything touching the DOM goes through execInTab with a pageXxx function. Those are injected into the page: no closures, inline every helper, and end the body with } catch (e) { return { __cc_err: e.message }; } — thrown exceptions are swallowed by chrome.scripting and surface as a useless "no result".
• Anything needing CDP (keyboard, eval, console, network, full-page screenshot) goes through ensureDebugger(tabId, [domains]) + cdp(tabId, method, params) instead.
• Element refs: read them from window.__cc_refs; a missing ref must produce a message telling Claude to call read_page again, matching the existing "stale ref" wording.
• Throw Error with an actionable message rather than returning error objects.

2. MCP tool — server/index.js

Inside buildMcpServer(), register with the same name as the handler key:

tool(
  "my_tool",
  "One line telling Claude when to reach for this and what it gets back.",
  {
    someArg: z.string().describe("..."),
    tabId: tabIdSchema,
  },
  async (args) => textResult(await call("my_tool", args))
);

Reuse tabIdSchema for tab targeting and textResult for the response. Pass a custom timeoutMs as the third arg of call() only for tools that can legitimately outrun the default 45s. Descriptions are read by the model at every session — say when to use the tool, not how it works.

3. E2E coverage — test/e2e.mjs

The test serves its own fixture pages from an in-process HTTP server and drives the real MCP client. Add an assertion next to the related tools: