MCP Builder

MCP Builder scaffolds a complete Model Context Protocol server you can run against Claude Desktop, the Claude CLI, or any MCP client — with tools, resources, and prompts already wired into the transport layer. It targets either the TypeScript SDK (@modelcontextprotocol/sdk) or the Python SDK (mcp / FastMCP), and ships the input schemas that stop a tool from silently returning malformed payloads. It's for developers who want a working server skeleton instead of copy-pasting from the spec.

When to use it

• You're exposing an internal API, database, or CLI to Claude as callable tools.
• You keep hitting the "tool ran but the model got garbage back" problem and want schema-validated arguments and return shapes.
• You want a server that speaks both stdio (for desktop clients) and HTTP/SSE without rewiring the transport yourself.
• You're prototyping a resource provider (files, records, docs) the model can read on demand.

What it does

The skill generates a project around the SDK's server primitives. In TypeScript that means a McpServer instance with server.tool(name, zodSchema, handler), server.resource(...), and server.prompt(...) registrations, plus a StdioServerTransport entry point. In Python it scaffolds a FastMCP app using @mcp.tool(), @mcp.resource("scheme://{id}"), and @mcp.prompt() decorators. Argument schemas are defined with Zod (TS) or Python type hints / Pydantic, so the runtime rejects bad input before your handler runs. You also get a package.json/pyproject.toml, a build/run script, and a ready-to-paste mcpServers config block for the client.

Usage

curl -fsSL --create-dirs -o ~/.claude/skills/mcp-builder/SKILL.md https://claudeskil.com/skills/mcp-builder/SKILL.md
# then, in your project:
claude "scaffold an MCP server in typescript with a tool
        called search_orders that takes a customer_id"

Generated TypeScript handler:

server.tool(
  "search_orders",
  { customer_id: z.string().describe("Customer UUID") },
  async ({ customer_id }) => ({
    content: [{ type: "text", text: await lookup(customer_id) }],
  })
);

Register it with the client:

{ "mcpServers": { "orders": { "command": "node", "args": ["dist/index.js"] } } }

Tips & gotchas

• Tools must return a content array (type: "text" | "image" | "resource"), not a bare string — the scaffold enforces this, but custom edits often break it.
• stdio transport reserves stdout for the protocol. Never console.log to stdout in a TS server; use console.error or a file logger.
• describe() on each Zod field becomes the parameter doc the model sees — fill them in, or tool selection degrades.
• Run npx @modelcontextprotocol/inspector against your server to test tools interactively before connecting a client.

FAQ

TypeScript or Python? Both produce equivalent servers. Pick TS for npm-distributed binaries, Python/FastMCP for fewer lines and quick scripts.

Does it support HTTP, not just stdio? Yes — request the streamable HTTP/SSE transport and the entry point is generated accordingly.

How do resources differ from tools? Resources are read-only context the model pulls by URI; tools perform actions and take arguments.