mcpster

A TypeScript SDK for building MCP servers — removes the boilerplate so you focus on what you expose, not how.

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Overview

mcpster is an agnostic TypeScript SDK for building Model Context Protocol (MCP) servers. It wraps @modelcontextprotocol/sdk behind a fluent, chainable API with Zod-first schema validation, URI template parsing, and consistent error handling. Servers built with mcpster start as local stdio processes and have a clear migration path to remote hosting and public npm distribution — without rewriting any business logic.

Features

• createServer() + chainable defineTool / defineResource / definePrompt API
• Zod schema validation enforced at tool registration time
• URI template parameter extraction for resources (templates://{name})
• Automatic error wrapping — handlers throw, mcpster returns MCP-compliant error responses
• Scope-aware server naming (project, user, or public scope)
• stdio and Streamable HTTP transports — switch with a single config field
• OAuth 2.1 (PKCE) support for protected remote servers — enable with auth: true
• Designed for progressive deployment: local stdio → remote Streamable HTTP → hosted → npm package

Installation

npm install mcpster

Usage

stdio (default)

import { createServer } from 'mcpster'
import { z } from 'zod'

createServer({ name: 'my-server', version: '1.0.0' })
  .defineTool({
    name: 'get_template',
    description: 'Retrieve a template by name',
    schema: z.object({ name: z.string() }),
    handler: async ({ name }) => { /* ... */ },
  })
  .defineResource({
    uri: 'templates://{name}',
    description: 'Template content by name',
    resolver: async ({ name }) => { /* ... */ },
  })
  .definePrompt({
    name: 'summarize',
    handler: async (args) => { /* ... */ },
  })
  .start() // stdio transport

Register the server per-project:

claude mcp add my-server -- npx mcpster start

Streamable HTTP transport

import { createServer } from 'mcpster'

createServer({
  name: 'my-server',
  version: '1.0.0',
  transport: 'http',
  http: { port: 3000, path: '/mcp' },
})
  .defineTool({ /* ... */ })
  .start() // listens on http://localhost:3000/mcp

Register with Claude Code:

claude mcp add --transport http my-server http://localhost:3000/mcp

OAuth 2.1 (protected remote server)

Enable auth: true to require clients to complete an OAuth 2.1 PKCE flow before accessing the MCP endpoint. Set baseUrl to your public server URL so OAuth discovery metadata points to the right place.

createServer({
  name: 'my-server',
  version: '1.0.0',
  transport: 'http',
  http: {
    port: 3000,
    path: '/mcp',
    auth: true,
    baseUrl: 'https://my-server.example.com',
  },
}).start()

mcpster handles the full OAuth flow: dynamic client registration (/register), authorization (/authorize), token issuance (/token), and bearer token verification on the MCP endpoint. All dynamically registered clients are treated as public PKCE clients — no pre-shared secrets required.

For persistence across restarts, point clientsFile at a file on a mounted volume:

http: {
  auth: true,
  baseUrl: 'https://my-server.example.com',
  clientsFile: '/data/oauth-clients.json',
}

Configuration

Option	Default	Description
name	required	Server name, used for MCP registration
version	required	Semver string
scope	process.cwd()	Project root; determines scope for naming and resource resolution
transport	'stdio'	Transport to use: 'stdio' or 'http'
http.port	3000	Port to listen on (HTTP transport only)
http.path	'/mcp'	Request path to handle (HTTP transport only)
http.auth	false	Enable OAuth 2.1 PKCE protection on the MCP endpoint
http.baseUrl	http://localhost:<port>	Public base URL — used for OAuth metadata and token endpoints
http.clientsFile	(in-memory)	Path to persist registered OAuth clients across restarts

Project Structure

mcpster/
├── src/
│   ├── index.ts              # Public API — re-exports createServer and types
│   ├── server.ts             # McpsterServer class — core orchestrator
│   ├── tool.ts               # defineTool — schema validation + handler wiring
│   ├── resource.ts           # defineResource — URI template matching + resolver
│   ├── prompt.ts             # definePrompt — prompt template registration
│   ├── transport/
│   │   ├── stdio.ts          # stdio transport adapter
│   │   └── http.ts           # Streamable HTTP transport adapter
│   ├── deploy/
│   │   ├── types.ts          # Shared DeployConfig, DeployResult, DeployAdapter types
│   │   ├── railway.ts        # Railway adapter (generateManifest, deploy)
│   │   ├── fly.ts            # Fly.io adapter (generateManifest, generateDockerfile, deploy)
│   │   ├── cloudflare.ts     # Cloudflare Workers adapter (generateManifest, generateWorkerShim, deploy)
│   │   └── cli.ts            # mcpster-deploy CLI entry point
│   └── types.ts              # Shared TypeScript types and interfaces
├── tests/
│   ├── server.test.ts
│   ├── tool.test.ts
│   ├── resource.test.ts
│   ├── prompt.test.ts
│   ├── transport.test.ts
│   └── deploy.test.ts
├── examples/
│   └── minimal/              # hello-mcp — tool + resource + prompt, runnable reference
├── package.json
└── tsconfig.json

Deploy (v3)

mcpster ships a deploy kit that pushes your Streamable HTTP server to Railway, Fly.io, or Cloudflare Workers with a single command. The Streamable HTTP transport must already be configured on your server before deploying — the deploy adapters wrap the existing transport: 'http' path.

Prerequisites

Target	Prerequisite
Railway	railway CLI installed and authenticated (railway login)
Fly.io	flyctl installed and authenticated (fly auth login)
Cloudflare Workers	wrangler installed and authenticated (wrangler login)

Usage

# Dry-run: print the generated manifest without deploying
npx mcpster-deploy --target railway --dry-run
npx mcpster-deploy --target fly --dry-run
npx mcpster-deploy --target cloudflare --dry-run

# Deploy
npx mcpster-deploy --target railway
npx mcpster-deploy --target fly --region lhr
npx mcpster-deploy --target cloudflare

All options:

-t, --target <target>    Deploy target (railway | fly | cloudflare)
-n, --name <name>        Server name (default: read from package.json)
-v, --version <version>  Server version (default: read from package.json)
-p, --port <port>        HTTP port (default: 3000)
-r, --region <region>    Preferred region — Fly.io only (default: iad)
-d, --dry-run            Print the generated manifest without deploying
-h, --help               Show help

Local → Hosted migration path

Stage 1 — Local stdio (no infrastructure)

createServer({ name: 'my-server', version: '1.0.0' }).start()

Stage 2 — Local Streamable HTTP (same server, different transport)

createServer({
  name: 'my-server',
  version: '1.0.0',
  transport: 'http',
  http: { port: 3000, path: '/mcp' },
}).start()

Stage 3 — Hosted (one command, no code changes)

npx mcpster-deploy --target railway
# → Deployed to Railway: https://my-server.up.railway.app

Then connect Claude Code to the deployed server:

claude mcp add --transport http my-server https://my-server.up.railway.app/mcp

The server code is identical across all three stages.

License

MIT

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