MCP

The MCP plugin turns each operation into a typed MCP tool that AI assistants can call. Each tool uses Zod schemas from @kubb/plugin-zod for its input and output.

Each tool handler calls the function a client plugin generates for that operation. The plugin writes server.ts, start.ts, and .mcp.json at the root of its output.path. start.ts calls the startServer() that server.ts exports, and .mcp.json runs start.ts to start a stdio server.

Installation

bun add -d @kubb/plugin-mcp

pnpm add -D @kubb/plugin-mcp

npm install --save-dev @kubb/plugin-mcp

yarn add -D @kubb/plugin-mcp

Or run kubb add plugin-mcp to install the version the Kubb registry pins and add pluginMcp() to kubb.config.ts.

Setup

• Add @kubb/plugin-ts, @kubb/plugin-zod, and a client plugin: @kubb/plugin-fetch or @kubb/plugin-axios. Leave sdk unset on the client plugin.
• Install @modelcontextprotocol/server v2 and zod 4.2 or a later v4 release in the app that runs the server. Add axios too when you use @kubb/plugin-axios.
• Install a TypeScript runner such as tsx. The generated .mcp.json runs npx tsx, which downloads tsx from npm when it is missing.
• Copy the server entry from the generated .mcp.json into the .mcp.json your MCP client reads, such as the one at the project root for Claude Code.

Options worth knowing

• client picks fetch or axios when both client plugins are registered. A single client is detected automatically.
• output.path must be a folder name, such as the default mcp, because single-file output has no place for server.ts, start.ts, and .mcp.json.

The args path in .mcp.json points at start.ts relative to the Kubb root, because MCP clients start the command from their own working directory. Use an absolute path for a client that starts in another folder, or point it at your own entry file to run setup code before startServer().

See Options for every option and its default.

Example

The config below generates an MCP server whose tools call the Petstore API through @kubb/plugin-fetch.

import { defineConfig } from 'kubb/config'
import { pluginTs } from '@kubb/plugin-ts'
import { pluginZod } from '@kubb/plugin-zod'
import { pluginFetch } from '@kubb/plugin-fetch'
import { pluginMcp } from '@kubb/plugin-mcp'

export default defineConfig({
  input: './petStore.yaml',
  output: { path: './src/gen' },
  plugins: [
    pluginTs(),
    pluginZod(),
    pluginFetch({ baseURL: 'https://petstore.swagger.io/v2' }),
    pluginMcp({ output: { path: 'mcp', mode: 'directory' } }),
  ],
})