MCP Resources

MCP resources provide data sources that AI models can read from. They support both static and parameterized URIs for flexible data access.

Creating Resources

Use pikkuMCPResourceFunc to create MCP resources:

import { pikkuMCPResourceFunc } from '../.pikku/pikku-types.gen.js'

export const getStaticResource = pikkuMCPResourceFunc(async ({ mcp }) => {
  return [
    {
      uri: mcp.uri!,
      text: JSON.stringify('Hello! This is a static resource.'),
    },
  ]
})

Parameterized Resources

Resources can accept parameters through URI templates:

import { NotFoundError } from '@pikku/core'

export const getUserInfo = pikkuMCPResourceFunc<{ userId: string }>(
  async (services, { userId }) => {
    services.logger.info(`Getting user info for: ${userId}`)

    // Mock user data - in a real app this would come from a database
    const mockUsers: Record<
      string,
      { userId: string; name: string; email: string; lastLogin: string }
    > = {
      '123': {
        userId: '123',
        name: 'John Doe',
        email: 'john@example.com',
        lastLogin: '2024-01-15T10:30:00Z',
      },
      '456': {
        userId: '456',
        name: 'Jane Smith',
        email: 'jane@example.com',
        lastLogin: '2024-01-14T15:45:00Z',
      },
    }

    const user = mockUsers[userId]
    if (!user) {
      throw new NotFoundError(`User not found: ${userId}`)
    }

    return [
      {
        uri: `getUserInfo/${userId}`,
        text: JSON.stringify(user),
      },
    ]
  }
)

Registering Resources

Register your resources in the routes file:

// mcp.routes.ts
import { addMCPResource } from '../.pikku/pikku-types.gen.js'
import { getStaticResource, getUserInfo } from './mcp.functions.js'

addMCPResource({
  uri: 'getStaticResource',
  title: 'Static Resource',
  description: 'Gets a static resource with predefined data',
  func: getStaticResource,
})

addMCPResource({
  uri: 'getUserInfo/{userId}',
  title: 'User Information',
  description: 'Retrieve user information by user ID',
  func: getUserInfo,
  tags: ['user', 'profile', 'data'],
})

Return Format

Resources return an array of resource objects:

return [
  {
    uri: 'resource-identifier',
    text: 'Resource content as text',
    // Optional: mimeType, blob for binary data
  },
]

Error Handling

Use Pikku's built-in error types for proper error responses:

import { NotFoundError, BadRequestError } from '@pikku/core'

if (!user) {
  throw new NotFoundError(`User not found: ${userId}`)
}