#Install the Weir skill / MCP server

Weir's product surface is a set of weir_* tools an agent calls — not a GUI. This page registers those tools in your agent host and verifies they loaded. Do this once per workspace, before Quickstart.

#Install

The toolkit ships as the npm package weir-toolkit. No account, no API key, no repo access:

npm install -g weir-toolkit

Note: These docs describe the v4 toolkit, which needs weir-toolkit >= 0.4.4 (the current published release). Run weir --version to check your installed version; do not copy a changing "latest" number from prose. The 0.4.0 release added weir experiment-ship-winner and the weir components-sync --check preflight; a toolkit older than 0.4.0 cannot run them. 0.4.5 is pending publish and will fix the package's bin alias so that npx -y weir-toolkit init works without the -p flag. If validation demands specVersion: 3 or rejects specVersion: 4 or a custom screen type, your toolkit is pre-v4. Upgrade it with npm install -g weir-toolkit@latest.

Or run it ad hoc with npx (no global install): npx -y -p weir-toolkit weir init is the canonical cold-start command for one-off verbs. From weir-toolkit 0.4.5 onward, npx -y weir-toolkit init works directly (no -p flag needed) once the bin-alias fix (roadmap 6.2) is published.

The package provides two commands: weir (the CLI — every tool as a subcommand) and weir-mcp (the MCP server — the identical tools over stdio for an agent host). The full tool list is on Reference → MCP tools. weir walk, weir conform, and weir release drive a real headless Chromium via Playwright — install the browser binary once:

npx playwright install chromium

#Register the MCP server

#Claude Code / any .mcp.json host

Add a server entry to .mcp.json at the workspace root:

{
  "mcpServers": {
    "weir": { "command": "npx", "args": ["-y", "-p", "weir-toolkit@latest", "weir-mcp"] }
  }
}

Restart the agent host so it re-reads .mcp.json. The -p flag is required — the package has two executables, and npx needs it to resolve weir-mcp.

#Cursor / other MCP clients

Use the client's MCP-server config UI or file: command npx, args ["-y", "-p", "weir-toolkit@latest", "weir-mcp"]. The transport is stdio.

#Verify the toolset loaded

Ask the host to list its tools. You must see the weir_* tools (weir_dev, weir_walk, weir_conform, weir_embed, weir_release, and the rest). If the list is empty, the server did not register — run npx -y -p weir-toolkit@latest weir-mcp by hand; it should sit silently waiting for a client (Ctrl-C to stop). If it errors instead, that error is the problem.

The CLI gives the same check without an agent host:

weir list

This prints every subcommand with its one-line description, straight from each tool's own description field. If you see the verb list (dev, walk, conform, embed, release, …), the toolkit is installed and current. That list is generated from the same source as the MCP tools, so it can never drift from what the server exposes.

#Use the CLI as the fallback surface

Every MCP tool maps to one CLI verb: the tool name with the weir_ prefix stripped and underscores turned to dashes (weir_app_status becomes app-status). Run any verb like this:

weir <verb> --fieldName value

Flags are --fieldName value, parsed against the same schema as the MCP tool. Array fields need a repeated flag, not space-separated values — pass --personas "" --personas "purchase=cancel", not --personas "" "purchase=cancel". Exit code is 0 on success, 1 on a tool error, so the CLI is safe in CI and && chains.

#React Native / Expo

Warning: Expo Go cannot load the required third-party native module. Use a development or release build.

#Next

• Scaffold a new app in one command: weir init — scaffold a new app.
• Author your first flow spec: Author your first flow.
• Run the whole loop with no account and no server URLs: Run everything locally.
• The full command loop: Quickstart.