MetaMask MCP

Instructions

Implementation Reference

• src/tools/sign-message.ts:14-35 (handler)

  The execute function implements the core logic of the 'sign-message' tool: extracts the message from args, calls wagmi's signMessage, returns the hash in a structured content response, with error handling.

  execute: async (args, { log }) => {
    try {
      const message = args.message;
      const result = await signMessage(wagmiConfig, {
        message,
      });
      return {
        content: [
          {
            type: "text",
            text: JSONStringify({
              hash: result,
            }),
          },
        ],
      };
    }
    catch (error) {
      log.debug((error as Error).message);
      throw error;
    }
  },

• src/tools/sign-message.ts:11-13 (schema)

  Zod schema defining the input parameters for the tool: a single 'message' string.

  parameters: z.object({
    message: z.string().describe("Message to sign."),
  }),

• src/tools/sign-message.ts:7-37 (registration)

  The registration function that adds the 'sign-message' tool to the FastMCP server using server.addTool, including name, description, schema, and handler.

  export function registerSignMessageTools(server: FastMCP, wagmiConfig: Config): void {
    server.addTool({
      name: "sign-message",
      description: "Sign a message.",
      parameters: z.object({
        message: z.string().describe("Message to sign."),
      }),
      execute: async (args, { log }) => {
        try {
          const message = args.message;
          const result = await signMessage(wagmiConfig, {
            message,
          });
          return {
            content: [
              {
                type: "text",
                text: JSONStringify({
                  hash: result,
                }),
              },
            ],
          };
        }
        catch (error) {
          log.debug((error as Error).message);
          throw error;
        }
      },
    });
  };

• src/tools/register-tools.ts:53-53 (registration)

  Top-level call to registerSignMessageTools within the central registerTools function, invoked as part of initializing all tools.

  registerSignMessageTools(server, wagmiConfig);