Typed tools. Composable servers.
A TypeScript toolkit for building MCP servers from reusable tools. Zod validation, request-scoped context, and stdio or HTTP transports, with optional JWT and Clerk authentication.
A reusable tool should not be tied to one server or transport. Tool authors also need a clear contract for validation, dependencies and authentication without rewriting those concerns for every handler.
I created and maintain Toolgrain: a TypeScript toolkit with reusable tool definitions, composable servers, context providers, transport adapters and optional authentication packages. The public repository includes documentation and runnable framework examples.
Conceptual map of the public toolkit. Select a step to explore the responsibilities; no remote tool is executed here.
Declare a reusable tool with a name, Zod schemas and a typed handler.
Combine tools with createServer() and attach the context providers and optional authentication needed by that server.
Expose tool discovery and execution through stdio, a managed Node HTTP listener, or Web and Node handlers.
Parse inputs, resolve request-cached context, run the handler and validate declared outputs.
A standalone tool() combines Zod schemas with a typed handler. createServer() composes those definitions into a server, with input and declared output parsing that honors schema defaults and transforms.
The same tool can be reused in different server compositions. Type inference supports authoring, while runtime validation checks the values crossing the tool boundary.
Lazy, typed context providers resolve dependencies on demand and cache them for the request.
Handlers can share request-scoped services and context without wiring the same dependency into each tool invocation by hand.
The packages provide stdio serving, a managed Node HTTP listener, Web and Node handlers, and optional JWT and Clerk authentication. Framework examples cover Express, Hono, Elysia and Next.js.
Tool definitions stay reusable as the hosting environment changes. Authentication can be added at the server boundary rather than repeated inside each handler.
Toolgrain is public under MIT, with published @toolgrain packages, documentation and runnable examples. The current protocol scope is tool discovery and execution over stdio and independent HTTP JSON POST requests. Sessions, SSE, resources and prompts are outside the current scope. No adoption or performance figures are claimed.