MCP: tool schema fixups

[connor4312]

Please add cases to this issue where you find tool schema scenarios that need to be fixed

• Having a {"type":"array" without a spec for items
• "VSCode support for MCP fails if any of the tools has a parameter declared as a restricted-size array. The SDK for MCP uses Zod for type description, and the z.tuple() type generator seems to map to an array of fixed size"

[digitarald]

Test case

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

const server = new McpServer({
  name: "Test MCP Server",
  version: "0.0.1"
});

server.tool("todays_quote",
            "Returns the quote of the day, based on a day of the week.",
            { dayName: z.string(), arg1: z.tuple([z.string(), z.record(z.any())]) },
            async ({ dayName }) => {
              const quotes = {
                monday: "Monday is the day that my coffee needs coffee.",
                tuesday: "Tuesday is the day I actually start the week.",
                wednesday: "Wednesday is like a math problem. It’s all about finding the right angle.",
                thursday: "Thursday is the new Friday.",
                friday: "Friday is a reminder that I survived the week.",
                saturday: "Saturday is for adventure.",
                sunday: "Sunday is a day of rest."
              };
              const key = dayName.toLowerCase() as keyof typeof quotes;
              return { content: [{ type: "text", text: quotes[key] || "Invalid day name." }] };
            }
          );

const transport = new StdioServerTransport();
await server.connect(transport);

[connor4312]

should be fixed off copilot chat main