Open source API development ecosystem - https://hoppscotch.io (open-source alternative to Postman, Insomnia)

Opensource IDE For Exploring and Testing Api's (lightweight alternative to postman/insomnia)

An interactive web UI for gRPC, along the lines of postman

Application Security Verification Standard

libopenapi is a fully featured, high performance OpenAPI 3.1, 3.0 and Swagger parser, library, validator and toolkit for golang applications.

An alternative to grpc_cli. giro can be used for gRPC servers without Server Reflection