{"version":"2.1.118","anchor":"mcp-tool-hooks-mcp-tool","canonical_anchor":"mcp-tool-hooks-mcp-tool","heading":"MCP Tool Hooks (mcp_tool)","tier":null,"area":null,"scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.118\/e\/mcp-tool-hooks-mcp-tool","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.118","markdown":"### MCP Tool Hooks (mcp_tool)\n\n**What**\n\nA new hook type that invokes an MCP server tool as the hook action, as an alternative to bash\/command hooks.\n\n**Details**\n\n- Configure with `type: \"mcp_tool\"` in hook definitions\n- Specify `server` (name of an already-configured MCP server) and `tool` (tool name on that server)\n- Supports `arguments` object with `${path}` interpolation from hook input JSON\n- Optional `timeout` field for per-call timeout in seconds\n- Reads `X-Mcp-Error-Code` header from 401 responses for better error diagnostics\n- Not available for all hook events \u2014 logs `\"mcp_tool hooks are not available for the '<event>' hook event\"` when unsupported\n\n**Evidence**\n\nHook type definition (search for `\"mcp_tool\"`) and MCP tool schema fields (search for `\"Name of an already-configured MCP server to invoke\"`)."}