io.github.cyanheads/mcp-ts-template

What is this?

@cyanheads/mcp-ts-core is the infrastructure layer for TypeScript MCP servers. Install it as a dependency — don't fork it. You write tools, resources, and prompts; the framework handles transports, auth, storage, config, logging, telemetry, and lifecycle.

import { createApp, tool, z } from '@cyanheads/mcp-ts-core';

const greet = tool('greet', {
  description: 'Greet someone by name and return a personalized message.',
  annotations: { readOnlyHint: true },
  input: z.object({ name: z.string().describe('Name of the person to greet') }),
  output: z.object({ message: z.string().describe('The greeting message') }),
  handler: async (input) => ({ message: `Hello, ${input.name}!` }),
});

await createApp({ tools: [greet] });

That's a complete MCP server. Every tool call is automatically logged with duration, payload sizes, memory usage, and request correlation — no instrumentation code needed. createApp() handles config parsing, logger init, transport startup, signal handlers, and graceful shutdown.

Quick start

bunx @cyanheads/mcp-ts-core init my-mcp-server
cd my-mcp-server
bun install

You get a scaffolded project with CLAUDE.md, Agent Skills, and a src/ tree ready for your tools. Infrastructure — transports, auth, storage, telemetry, lifecycle, linting — lives in node_modules. What's left is domain: which APIs to wrap, which workflows to expose.

Start your coding agent (Claude Code, Codex, Cursor), describe the system you want to expose, and it drives the build. The included skills cover the full cycle: setup, design-mcp-server, scaffolding, testing, release.

What you get

Here's what tool definitions look like:

import { tool, z } from '@cyanheads/mcp-ts-core';

export const search = tool('search', {
  description: 'Search for items by query.',
  input: z.object({
    query: z.string().describe('Search query'),
    limit: z.number().default(10).describe('Max results'),
  }),
  output: z.object({ items: z.array(z.string()).describe('Search results') }),
  async handler(input) {
    const results = await doSearch(input.query, input.limit);
    return { items: results };
  },
});

And resources:

import { resource, z } from '@cyanheads/mcp-ts-core';

export const itemData = resource('items://{itemId}', {
  description: 'Retrieve item data by ID.',
  params: z.object({ itemId: z.string().describe('Item ID') }),
  async handler(params, ctx) {
    return await getItem(params.itemId);
  },
});

Everything registers through createApp() in your entry point:

await createApp({
  name: 'my-mcp-server',
  version: '0.1.0',
  tools: allToolDefinitions,
  resources: allResourceDefinitions,
  prompts: allPromptDefinitions,
});

It also works on Cloudflare Workers with createWorkerHandler() — same definitions, different entry point.

Features

• Declarative definitions — tool(), resource(), prompt() builders with Zod schemas. appTool()/appResource() add interactive HTML UIs.
• Unified Context — one ctx for logging, tenant-scoped storage, elicitation, sampling, cancellation, and task progress.
• Inline auth — auth: ['scope'] on definitions. Framework checks scopes before dispatch — no wrapper code.
• Task tools — task: true for long-running ops; framework manages create/poll/progress/complete/cancel.
• Definition linter — validates names, schemas, auth scopes, annotation coherence, and format-parity at startup. Standalone CLI (lint:mcp) and devcheck step.
• Structured errors — handlers throw; framework catches, classifies, and formats. Error factories (notFound(), validationError(), …) when the code matters.
• Multi-backend storage — in-memory, filesystem, Supabase, Cloudflare D1/KV/R2. Swap providers via env var; handlers don't change.
• Pluggable auth — none, jwt, or oauth. Local secret or JWKS verification.
• Observability — Pino logging, optional OpenTelemetry traces and metrics. Request correlation and tool metrics are automatic.
• Local + edge — same definitions run on stdio, HTTP (Hono), and Cloudflare Workers.
• Tiered dependencies — parsers, OTEL SDK, Supabase, and OpenAI are optional peers. Install what you use.
• Agent-first DX — ships CLAUDE.md with the full exports catalog so AI agents ramp up without prompting.

Server structure

my-mcp-server/
  src/
    index.ts                              # createApp() entry point
    worker.ts                             # createWorkerHandler() (optional)
    config/
      server-config.ts                    # Server-specific env vars
    services/
      [domain]/                           # Domain services (init/accessor pattern)
    mcp-server/
      tools/definitions/                  # Tool definitions (.tool.ts)
      resources/definitions/              # Resource definitions (.resource.ts)
      prompts/definitions/                # Prompt definitions (.prompt.ts)
  package.json
  tsconfig.json                           # extends @cyanheads/mcp-ts-core/tsconfig.base.json
  CLAUDE.md                               # Points to core's CLAUDE.md for framework docs

No src/utils/, no src/storage/, no src/types-global/, no src/mcp-server/transports/ — infrastructure lives in node_modules.

Configuration

All core config is Zod-validated from environment variables. Server-specific config uses a separate Zod schema with lazy parsing.

See CLAUDE.md for the full configuration reference.

API overview

Entry points

Builders

Context

Handlers receive a unified Context object:

Subpath exports

import { createApp, tool, resource, prompt } from '@cyanheads/mcp-ts-core';
import { createWorkerHandler } from '@cyanheads/mcp-ts-core/worker';
import { McpError, JsonRpcErrorCode, notFound, serviceUnavailable } from '@cyanheads/mcp-ts-core/errors';
import { checkScopes } from '@cyanheads/mcp-ts-core/auth';
import { markdown, fetchWithTimeout } from '@cyanheads/mcp-ts-core/utils';
import { OpenRouterProvider, GraphService } from '@cyanheads/mcp-ts-core/services';
import { validateDefinitions } from '@cyanheads/mcp-ts-core/linter';
import { createMockContext } from '@cyanheads/mcp-ts-core/testing';
import { fuzzTool, fuzzResource, fuzzPrompt } from '@cyanheads/mcp-ts-core/testing/fuzz';

See CLAUDE.md for the complete exports reference.

Examples

The examples/ directory contains a reference server consuming core through public exports, demonstrating all patterns:

Testing

import { createMockContext } from '@cyanheads/mcp-ts-core/testing';
import { myTool } from '@/mcp-server/tools/definitions/my-tool.tool.js';

const ctx = createMockContext({ tenantId: 'test-tenant' });
const input = myTool.input.parse({ query: 'test' });
const result = await myTool.handler(input, ctx);

createMockContext() provides stubbed log, state, and signal. Pass { tenantId } for state operations, { sample } for LLM mocking, { elicit } for elicitation mocking, { progress: true } for task tools.

Fuzz testing

Schema-aware fuzz testing via fast-check. Generates valid inputs from Zod schemas and adversarial payloads (prototype pollution, injection strings, type confusion) to verify handler invariants.

import { fuzzTool } from '@cyanheads/mcp-ts-core/testing/fuzz';

const report = await fuzzTool(myTool, { numRuns: 100 });
expect(report.crashes).toHaveLength(0);
expect(report.leaks).toHaveLength(0);
expect(report.prototypePollution).toBe(false);

Also exports fuzzResource, fuzzPrompt, zodToArbitrary, and ADVERSARIAL_STRINGS for custom property-based tests.

Documentation

• CLAUDE.md — Framework reference: exports catalog, patterns, Context interface, error codes, auth, config, testing. Ships in the npm package.
• CHANGELOG.md — Version history

Development

bun run rebuild        # clean + build (scripts/clean.ts + scripts/build.ts)
bun run devcheck       # lint, format, typecheck, MCP defs, audit, outdated
bun run lint:mcp       # validate MCP definitions against spec
bun run test:all       # vitest (unit + integration)

Contributing

Issues and pull requests welcome. Run checks before submitting:

bun run devcheck
bun run test:all

License

Apache 2.0 — see LICENSE.