Config MCP Server

Instructions

Implementation Reference

• src/index.ts:66-76 (handler)

  Handler function for the 'getConfig' tool. Reads the configuration file using readConfigFile helper and optionally extracts a value at a dot-separated key path, returning the result as JSON string or error.

  async ({ file, key }: { file: string; key?: string }) => {
    try {
      const data = await readConfigFile(file);
      const value = key
        ? key.split(".").reduce((o: any, k: string) => (o ? o[k] : undefined), data)
        : data;
      return { content: [{ type: "text", text: JSON.stringify(value, null, 2) }] };
    } catch (error) {
      return { content: [{ type: "text", text: `Error reading config: ${error}` }], isError: true };
    }
  }

• src/index.ts:62-65 (schema)

  Zod input schema defining parameters for getConfig: 'file' (required path string) and 'key' (optional dot-separated path string).

  {
    file: z.string().describe("Path to the configuration file"),
    key: z.string().optional().describe("Optional dot-separated key path (e.g., 'database.host')"),
  },

• src/index.ts:59-77 (registration)

  MCP tool registration for 'getConfig', including name, description, input schema, and inline handler implementation.

  mcp.tool(
    "getConfig",
    "Read a configuration file (JSON/JSONC/YAML/TOML) and optionally extract a specific key",
    {
      file: z.string().describe("Path to the configuration file"),
      key: z.string().optional().describe("Optional dot-separated key path (e.g., 'database.host')"),
    },
    async ({ file, key }: { file: string; key?: string }) => {
      try {
        const data = await readConfigFile(file);
        const value = key
          ? key.split(".").reduce((o: any, k: string) => (o ? o[k] : undefined), data)
          : data;
        return { content: [{ type: "text", text: JSON.stringify(value, null, 2) }] };
      } catch (error) {
        return { content: [{ type: "text", text: `Error reading config: ${error}` }], isError: true };
      }
    }
  );

• src/lib/files.ts:19-34 (helper)

  Helper function that reads and parses configuration files in supported formats (JSON, JSONC, YAML/YML, TOML) by detecting the file extension and using appropriate parsers.

  export async function readConfigFile(file: string): Promise<any> {
    const fmt = detectFormat(file);
    const content = await fs.readFile(file, "utf8");
    switch (fmt) {
      case "yaml":
      case "yml":
        return parseYaml(content);
      case "toml":
        return TOML.parse(content);
      case "jsonc":
        return parseCommentJson(content);
      case "json":
      default:
        return JSON.parse(content);
    }
  }