Medusa MCP Server

Instructions

Implementation Reference

• src/index.ts:34-42 (registration)

  Registers all dynamically generated tools from Medusa store and admin services, including the 'PostCarts' tool, with the MCP server using server.tool(name, description, inputSchema, handler).
  tools.forEach((tool) => { server.tool( tool.name, tool.description, tool.inputSchema, tool.handler ); });
• src/services/medusa-store.ts:83-127 (handler)

  The handler function that executes the logic for all store API tools, including PostCarts. It prepares query/body from input based on OpenAPI parameters and calls the Medusa SDK client.fetch with appropriate method (POST for PostCarts).
  handler: async ( input: InferToolHandlerInput<any, ZodTypeAny> ): Promise<any> => { const query = new URLSearchParams(input); const body = Object.entries(input).reduce( (acc, [key, value]) => { if ( parameters.find( (p) => p.name === key && p.in === "body" ) ) { acc[key] = value; } return acc; }, {} as Record<string, any> ); if (method === "get") { console.error( `Fetching ${refPath} with GET ${query.toString()}` ); const response = await this.sdk.client.fetch(refPath, { method: method, headers: { "Content-Type": "application/json", "Accept": "application/json", "Authorization": `Bearer ${process.env.PUBLISHABLE_KEY}` }, query: query }); return response; } else { const response = await this.sdk.client.fetch(refPath, { method: method, headers: { "Content-Type": "application/json", "Accept": "application/json", "Authorization": `Bearer ${process.env.PUBLISHABLE_KEY}` }, body: JSON.stringify(body) }); return response; } } };
• src/services/medusa-store.ts:54-82 (schema)

  Dynamically generates the Zod inputSchema for the tool based on the OpenAPI parameters from store.json spec, used for PostCarts input validation.
  inputSchema: { ...parameters .filter((p) => p.in != "header") .reduce((acc, param) => { switch (param.schema.type) { case "string": acc[param.name] = z.string().optional(); break; case "number": acc[param.name] = z.number().optional(); break; case "boolean": acc[param.name] = z.boolean().optional(); break; case "array": acc[param.name] = z .array(z.string()) .optional(); break; case "object": acc[param.name] = z.object({}).optional(); break; default: acc[param.name] = z.string().optional(); } return acc; }, {} as any) },
• src/services/medusa-store.ts:30-129 (helper)

  wrapPath method creates the tool definition (name, description, schema, handler) for each OpenAPI path, specifically extracting 'PostCarts' as name from operationId for POST /store/carts.
  wrapPath(refPath: string, refFunction: SdkRequestType) { return defineTool((z): any => { let name; let description; let parameters: Parameter[] = []; let method = "get"; if ("get" in refFunction) { method = "get"; name = refFunction.get.operationId; description = refFunction.get.description; parameters = refFunction.get.parameters; } else if ("post" in refFunction) { method = "post"; name = refFunction.post.operationId; description = refFunction.post.description; parameters = refFunction.post.parameters ?? []; } if (!name) { throw new Error("No name found for the function"); } return { name: name!, description: description, inputSchema: { ...parameters .filter((p) => p.in != "header") .reduce((acc, param) => { switch (param.schema.type) { case "string": acc[param.name] = z.string().optional(); break; case "number": acc[param.name] = z.number().optional(); break; case "boolean": acc[param.name] = z.boolean().optional(); break; case "array": acc[param.name] = z .array(z.string()) .optional(); break; case "object": acc[param.name] = z.object({}).optional(); break; default: acc[param.name] = z.string().optional(); } return acc; }, {} as any) }, handler: async ( input: InferToolHandlerInput<any, ZodTypeAny> ): Promise<any> => { const query = new URLSearchParams(input); const body = Object.entries(input).reduce( (acc, [key, value]) => { if ( parameters.find( (p) => p.name === key && p.in === "body" ) ) { acc[key] = value; } return acc; }, {} as Record<string, any> ); if (method === "get") { console.error( `Fetching ${refPath} with GET ${query.toString()}` ); const response = await this.sdk.client.fetch(refPath, { method: method, headers: { "Content-Type": "application/json", "Accept": "application/json", "Authorization": `Bearer ${process.env.PUBLISHABLE_KEY}` }, query: query }); return response; } else { const response = await this.sdk.client.fetch(refPath, { method: method, headers: { "Content-Type": "application/json", "Accept": "application/json", "Authorization": `Bearer ${process.env.PUBLISHABLE_KEY}` }, body: JSON.stringify(body) }); return response; } } }; }); }
• src/utils/define-tools.ts:16-60 (helper)

  defineTool utility wraps the tool handler to format output as MCP CallToolResult content and handle errors appropriately.
  export const defineTool = ( cb: (zod: typeof z) => ToolDefinition<any, ZodAny, any> ) => { const tool = cb(z); const wrappedHandler = async ( input: InferToolHandlerInput<Zod.ZodAny, Zod.ZodAny>, _: RequestHandlerExtra ): Promise<{ content: CallToolResult["content"]; isError?: boolean; statusCode?: number; }> => { try { const result = await tool.handler(input); return { content: [ { type: "text", text: JSON.stringify(result, null, 2) } ] }; } catch (error) { return { content: [ { type: "text", text: `Error: ${ error instanceof Error ? error.message : String(error) }` } ], isError: true }; } }; return { ...tool, handler: wrappedHandler }; };