Serve Resources and Prompts

Until you serve a resource, a host cannot read your document. Until you serve a prompt, a host cannot start from that prompt.

Define Resources and Prompts#

1. Define each document with resourceDefinition.
2. Define each prompt with promptDefinition.
3. Pass resources and prompts to createMCPServer.

import {
  createMCPServer,
  promptDefinition,
  resourceDefinition,
} from '@tanstack/ai-mcp/server'
import { z } from 'zod'

const readme = resourceDefinition({
  name: 'readme',
  mimeType: 'text/markdown',
  uri: 'file:///readme.md',
}).read(async () => ({ text: '# Hello' }))

const file = resourceDefinition({
  name: 'file',
  mimeType: 'text/plain',
  uriTemplate: 'file:///{path}',
}).read(async () => ({ text: 'file body' }))

const summarize = promptDefinition({
  name: 'summarize',
  description: 'Summarize a topic',
  argsSchema: z.object({ topic: z.string() }),
}).render(async (args) => [{ role: 'user', content: args.topic }])

const server = createMCPServer({
  name: 'library',
  version: '1.0.0',
  resources: [readme, file],
  prompts: [summarize],
})

export function handleMcp(request: Request) {
  return server.fetch(request)
}

Resources#

A resource must have uri or uriTemplate.

• uri: one document. An example is file:///readme.md.
• uriTemplate: a URI pattern. An example is file:///{path}.

If the resource has no uri and no uriTemplate, resourceDefinition throws This resource has no uri and no uriTemplate. Pass a uri or a uriTemplate.

If you pass uri and uriTemplate, the server uses uri.

read takes no arguments. read returns { text } for a text document. For a binary document, read returns { blob } with a base64 string.

Prompts#

argsSchema.parse runs first. Then render receives the parsed arguments.

render returns an array of messages. Each message has these fields:

• role: user or assistant.
• content: the message text.

If role is not user or assistant, the server sends that message as user.

What the Host Gets#

The host reads file:///readme.md. The text is # Hello.

The host starts from the summarize prompt with topic weather. The role is user. The content string is weather.