managing-mcp-servers

Managing MCP servers in ThinkRail

ThinkRail uses pi's built-in MCP support but has no pi executable. Never run pi mcp add, pi mcp login or other pi commands; edit the configuration files and point the user at Settings › MCP servers for everything that needs them.

Where servers are configured

• User level — pi's agent directory, usually ~/.pi/agent/mcp.json: available in every project.
• This repository — .pi/mcp.json in the worktree, tracked in git. A server defined here does not run until the user approves it in Settings, and any later change to its entry needs approval again. It only loads when the user trusts the project.

Both files use pi's format:

{
  "mcpServers": {
    "docs": { "url": "https://example.com/mcp" },
    "browser": { "command": "npx", "args": ["-y", "@playwright/[email protected]"] }
  }
}

• Pin package versions in args; never @latest.
• Never write a secret into either file. Reference it as ${ENV_VAR} (from the host's environment) or !command (the command's output, for example !gh auth token), or let the user sign in.
• exposure: deferred (the default here — load the server's tools with tool_search first), direct (a few always-useful tools), or hidden. codemode is treated as deferred.
• Prefer the user-level file for personal servers; only put a server in .pi/mcp.json when the user wants it shared with the repository.

GitHub

GitHub is a recipe, not a preset: its hosted server, authenticated with the user's GitHub CLI sign-in. Add it to the user-level file (Settings › MCP servers offers the same entry under Paste JSON):

{
  "mcpServers": {
    "github": {
      "url": "https://api.githubcopilot.com/mcp/readonly",
      "headers": { "Authorization": "!t=$(gh auth token) && echo \"Bearer $t\"" }
    }
  }
}

• /readonly is GitHub's documented read-only mode (same as an X-MCP-Readonly: true header). Use https://api.githubcopilot.com/mcp/ only when the user asks for tools that change data.
• The header command runs each time a chat connects. While gh is logged out it fails instead of sending an empty token; the user runs gh auth login in a terminal.
• Unverified: whether GitHub accepts the GitHub CLI token's scopes for every toolset. If the server rejects it, ask the user for a token in an environment variable: "Authorization": "Bearer ${GITHUB_TOKEN}".