contract

contract is an OCaml library for describing HTTP API contracts as typed values. The current code covers a small pure core: endpoint definitions, path matching, scalar and JSON decoding, request and response validation, and OpenAPI output.

Current MVP

The current source tree is a thin vertical slice for REST-style JSON APIs. It has no HTTP server dependency. A request is a value passed to the validator; a response is a status plus optional JSON body checked against the endpoint's declared responses. Path parameters are percent-decoded after route matching.

Released package:

opam install contract

See examples/users_api.ml for a small users API with GET /users/:id and POST /users.

dune exec examples/users_api.exe

Development:

dune build @all
dune runtest
dune fmt

Current limitations:

• no real HTTP adapter yet
• no typed client yet
• no OpenAPI import yet
• no mock server yet