Eio concurrency patterns for OCaml applications. Use when Claude needs to: (1) Write concurrent OCaml code with Eio, (2) Handle network operations with cohttp-eio, (3) Manage resource lifecycles with switches, (4) Implement rate limiting or synchronization, (5) Create parallel operations with fibers, (6) Test async code with Eio_mock, (7) Integrate with bytesrw for streaming, or any other Eio-based concurrency tasks

JSON type-safe encoding and decoding using the OCaml jsont library. Use when Claude needs to: define typed JSON codecs for OCaml record types, parse JSON strings to OCaml values, or serialize OCaml values to JSON, or work with nested JSON structures