Regression in 1.11.1: not assigning tool arguments in schema

[kirk-marple]

When defining a tool in 1.11.1, the tool arguments don't appear on the MCP client.

However, using 1.10.2, they do.

Something must have broken between these two versions.

    server.tool(
    "searchMcpServers",
    `Retrieve relevant MCP Servers and Tools from McPoogle search engine. Use this tool to find MCP Servers and Tools that match a given user prompt. The search results will include the name, description, and GitHub URL of each MCP Server.
    Accepts an LLM user prompt for content retrieval. For best retrieval quality, provide only key words or phrases from the user prompt, which will be used to create text embeddings for a vector search query.
    Returns the ranked content sources, including their content resource URI to retrieve the complete Markdown text.`,
    { 
        prompt: z.string().describe("LLM user prompt for MCP search.")
    },
    async ({ prompt }) => {
[removed]
    }
    );   

For more detail, see issue in Vercel MCP adapter repo.

vercel-labs/mcp-for-next.js#9

[axel-rock]

Someone from Vercel pointed me to this issue, it appears that I have the same issue. Using 1.10.2 brings back the arguments.

If that helps, I have a basic reproduction using SvelteKit's boilerplate here: https://github.com/axel-rock/sveltekit-mcp

[bohdan-romanchenko]

This fragment is returning false once argument where passed via @vercel/mcp-adapter server.tool function.

const isZodRawShape = (obj: unknown): obj is ZodRawShape => {
  if (typeof obj !== "object" || obj === null) return false;

  const isEmptyObject = z.object({}).strict().safeParse(obj).success;

  // Check if object is empty or at least one property is a ZodType instance
  return isEmptyObject || Object.values(obj as object).some(v => v instanceof ZodType);
};

Particularly this part is returning false: Object.values(obj as object).some(v => v instanceof ZodType).

The argument could be like this:

const t = server.tool(
  "echo",
  "Echo a message",
  { message: z.string() },
  async ({ message }) => ({
    content: [{ type: "text", text: `Tool echo: ${message}` }],
  })
);

Once I try the same isZodRawShape in the same server execution or in tests - it works correctly, but the integration part is failing in some moment.

[bohdan-romanchenko]

Seems to be resolved here #468

[axel-rock]

I confirm that it works with 1.11.2 🙏