One TypeScript route → typed SDK, docs, OpenAPI, and MCP.

For humans: callspec.logfox.ai · Try the demo

Most teams duct-tape the same API across REST routes, OpenAPI specs, DIY clients, docs, types, validators and MCP. That's a ton of repetitive work and brittle code that drifts. Instead, define each route once in TypeScript — inputs, outputs, and errors — and Callspec ships the server, SDK, docs, OpenAPI, and MCP from that contract. One source of truth, unit-testable, no drift. On the frontend you call `api.searchPosts({…})` and get a **Result** back — success value or a typed error `code` you can switch on. Same methods, same types, same errors as the server and as agents on MCP. Unit-test the real handler with `.handler(input, ctx)` — no HTTP, no `req`/`res`. ## Quick start ```bash npm i callspec runtyp express ``` [Getting started](src/content/docs/getting-started.md) walks through a route, `spec()`, `mountSpec()`, and the generated client. For a minimal one-file spike, see [Single-file server example](src/content/docs/single-file-server-example.md). ## Coding agents Optional — for Cursor, Claude Code, and similar tools: [`skills/callspec/SKILL.md`](skills/callspec/SKILL.md) (rules) and [copy-paste prompts](src/content/docs/coding-agents.md). The guides below are the source of truth for the API. ## Contents Same guides as [callspec.logfox.ai](https://callspec.logfox.ai). Links are repo-relative — they work in a checkout and on GitHub’s file browser. ### Introduction - [Single-file server example](src/content/docs/single-file-server-example.md) - [Getting started](src/content/docs/getting-started.md) - [Server layout](src/content/docs/server-layout.md) - [Unit testing](src/content/docs/unit-testing.md) - [Try the demo locally](src/content/docs/try-the-demo-locally.md) ### API reference - [`route`](src/content/docs/api-reference/route.md) - [`spec`](src/content/docs/api-reference/spec.md) - [`mountSpec`](src/content/docs/api-reference/mount-spec.md) - [Auth and scope](src/content/docs/api-reference/auth-and-scope.md) - [Surfaces & exports](src/content/docs/api-reference/surfaces-and-exports.md) - [Builtin errors](src/content/docs/builtin-errors.md) ### Working with Coding Agents - [Skill & prompts](src/content/docs/coding-agents.md) ### Server - [Authentication](src/content/docs/authentication.md) - [Request context](src/content/docs/request-context.md) - [Error handling](src/content/docs/error-handling.md) - [File uploads](src/content/docs/file-uploads.md) - [Outside Callspec](src/content/docs/outside-callspec.md) ### Client - [SDK generation](src/content/docs/sdk-generation.md) - [Client usage](src/content/docs/client-usage.md) - [Shared validation](src/content/docs/shared-validation.md) ### Docs UI - [Overview](src/content/docs/docs-ui.md) - [Branding](src/content/docs/docs-ui-branding.md) - [Hosting (CloudFront / Pages)](src/content/docs/hosting-cloudfront-pages.md) ### MCP Server - [Overview](src/content/docs/mcp.md) ### OpenAPI - [Overview](src/content/docs/openapi.md) - [Multi-language SDKs](src/content/docs/multi-language-sdks.md) ### Project - [Development](src/content/docs/development.md)