From existing function to MCP tool

Wrap your existing logic with act.action() to make it MCP-ready.

// your existing function
async function getDoughnuts({ userId, limit }: { userId: string; limit?: number }) {
  return db.doughnuts.findMany({ where: { userId }, take: limit ?? 10 });
}

// register it — now MCP-ready
export const getDoughnuts = act.action({
  id: 'getDoughnuts',
  description: 'Get doughnuts for a user',
  input: z.object({
    userId: z.string(),
    limit: z.number().optional(),
  }),
  handler: async ({ userId, limit }) => {
    return db.doughnuts.findMany({ where: { userId }, take: limit ?? 10 });
  },
});

// your app
await getDoughnuts({ userId: '123', limit: 5 });

// an MCP agent
// → calls getDoughnuts with { userId: '123', limit: 5 }

No new server. No separate process. No MCP knowledge required.

Install

npx @act-sdk/cli init

Or manually:

npm install @act-sdk/core @act-sdk/mcp @act-sdk/adapters zod

Next.js Integration

1. Wrap your existing logic (lib/actions/doughnuts.ts)

import { z } from 'zod';
import { act } from '@/act-sdk.config';

export const getDoughnuts = act.action({
  id: 'getDoughnuts',
  description: 'Get doughnuts for the authenticated user',
  input: z.object({ limit: z.number().optional() }),
  handler: async ({ limit }, context) => {
    return db.doughnuts.findMany({
      where: { userId: context?.authInfo.userId },
      take: limit ?? 10,
    });
  },
});

export const orderDoughnut = act.action({
  id: 'orderDoughnut',
  description: 'Order a doughnut for the authenticated user',
  input: z.object({ flavour: z.string() }),
  handler: async ({ flavour }, context) => {
    return db.orders.create({
      data: { flavour, userId: context?.authInfo.userId },
    });
  },
});

2. Config File (act-sdk.config.ts)

import { createAct, defineConfig } from '@act-sdk/core';

export const act = createAct();

export default defineConfig({
  name: 'my-app',
  description: 'My app MCP server',
  version: '1.0.0',
  act,
});

3. Add the route (app/api/mcp/route.ts)

import { createNextHandler } from '@act-sdk/adapters/nextjs';
import config from '@/act-sdk.config';

export const { GET, POST, DELETE } = createNextHandler(config, {
  auth: async (req) => {
    const token = req.headers.get('authorization')?.split(' ')[1];
    if (!token) return null;
    return verifyJWT(token);
  },
});

STDIO

import { createStdioServer } from '@act-sdk/adapters/stdio';
import config from './act-sdk.config.js';

createStdioServer(config);

Packages

Package	Purpose
@act-sdk/core	Action registry, createAct(), defineConfig()
@act-sdk/mcp	Translates actions into MCP tools
@act-sdk/adapters	Next.js and STDIO adapters

Contribute to other frameworks

Help us expand Act SDK to more ecosystems. If you want support for Express, Hono, Fastify, or another framework, open an issue or contribute an adapter.

Open an Issue

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