Ai Sdk Tool To

License: MIT TypeScript

A simple wrapper function to convert AI SDK tools to FastMCP tools.

Overview

This is a tiny utility that converts AI SDK tool definitions to FastMCP tool format:

• ✨ Simple wrapper function - just one function: toFastMCPTool()
• 🔄 Preserve type safety with full TypeScript support
• 🛠️ Handle errors gracefully with automatic error wrapping
• 📦 Zero dependencies - only peer dependencies you already have

Installation

bun add @tengis617/ai-sdk-tool-to-mcp
# or
npm install @tengis617/ai-sdk-tool-to-mcp

Peer dependencies (install if you don't already have them):

bun add ai zod fastmcp

Quick Start

import { tool } from 'ai';
import { z } from 'zod';
import { FastMCP } from 'fastmcp';
import { toFastMCPTool } from '@tengis617/ai-sdk-tool-to-mcp';

// Define your AI SDK tool
const weatherTool = tool({
  description: 'Get the current weather in a given location',
  inputSchema: z.object({
    location: z.string().describe('The city and state, e.g. San Francisco, CA'),
    unit: z.enum(['celsius', 'fahrenheit']).optional().default('fahrenheit'),
  }),
  execute: async ({ location, unit }) => {
    return { location, temperature: 72, unit, conditions: 'Sunny' };
  },
});

// Convert to FastMCP tool and add to server
const server = new FastMCP({ name: 'my-server', version: '1.0.0' });
server.addTool(toFastMCPTool('weather', weatherTool));

server.start({ transportType: 'stdio' });

Usage

Basic Example

import { tool } from 'ai';
import { z } from 'zod';
import { FastMCP } from 'fastmcp';
import { toFastMCPTool } from '@tengis617/ai-sdk-tool-to-mcp';

const calculatorTool = tool({
  description: 'Perform basic arithmetic operations',
  inputSchema: z.object({
    operation: z.enum(['add', 'subtract', 'multiply', 'divide']),
    a: z.number(),
    b: z.number(),
  }),
  execute: async ({ operation, a, b }) => {
    switch (operation) {
      case 'add': return { result: a + b };
      case 'subtract': return { result: a - b };
      case 'multiply': return { result: a * b };
      case 'divide': 
        if (b === 0) throw new Error('Division by zero');
        return { result: a / b };
    }
  },
});

const server = new FastMCP({
  name: 'calculator-server',
  version: '1.0.0',
});

// Convert and add the tool
server.addTool(toFastMCPTool('calculator', calculatorTool));

server.start({ transportType: 'stdio' });

Multiple Tools

Add multiple tools to your server:

const server = new FastMCP({
  name: 'my-tools',
  version: '1.0.0',
});

server.addTool(toFastMCPTool('weather', weatherTool));
server.addTool(toFastMCPTool('calculator', calculatorTool));
server.addTool(toFastMCPTool('search', searchTool));

server.start({ transportType: 'stdio' });

Complex Schemas

The wrapper handles complex Zod schemas automatically:

const createUserTool = tool({
  description: 'Create a new user',
  inputSchema: z.object({
    username: z.string().min(3).max(20),
    profile: z.object({
      firstName: z.string(),
      lastName: z.string(),
      email: z.string().email(),
      age: z.number().optional(),
    }),
    tags: z.array(z.string()).default([]),
  }),
  execute: async (params) => {
    return {
      id: crypto.randomUUID(),
      ...params,
      createdAt: new Date().toISOString(),
    };
  },
});

server.addTool(toFastMCPTool('createUser', createUserTool));

API Reference

toFastMCPTool(name: string, aiTool: AISDKTool): FastMCPTool

Converts an AI SDK tool to a FastMCP tool.

Parameters:

• name (string): The name of the tool
• aiTool (AISDKTool): An AI SDK tool object created with tool() from the ai package

Returns: A FastMCP tool object that can be passed to server.addTool()

What it does:

• Passes through the Zod schema (both AI SDK and FastMCP use Zod natively)
• Wraps the AI SDK execute function to work with FastMCP's calling convention
• Handles errors and wraps them with helpful messages
• Converts results to JSON strings as expected by FastMCP

How It Works

This is a simple wrapper that adapts AI SDK tools to FastMCP's interface:

1. Schema: Passes the Zod schema directly (no conversion needed - both use Zod!)
2. Execution: Wraps the AI SDK execute function to provide the context object it expects
3. Error Handling: Catches errors and wraps them with helpful messages
4. Result Formatting: Converts the result to a JSON string as FastMCP expects

Examples

Check out the examples directory:

• basic-stdio.ts - Basic stdio server example
• server.ts - Full server with multiple tools

Run examples with:

bun run examples/basic-stdio.ts
bun run examples/server.ts

Use Cases

• Expose AI SDK tools to MCP clients (Claude Desktop, Cline, etc.)
• Quick MCP servers: Turn your existing AI SDK tools into MCP servers
• Tool sharing: Use the same tool definitions across AI SDK and FastMCP applications

Contributing

Contributions are welcome! See CONTRIBUTING.md for guidelines.

License

MIT License - see LICENSE file for details

Related

• AI SDK - Vercel's AI SDK for building AI-powered applications
• FastMCP - Fast, simple MCP server framework
• Model Context Protocol - Protocol for connecting AI models with external context