OpenAPI
Witness's endpoints are straightforward and don't involve any advanced encoding schema; this means it's fairly easy to integrate witih Witness regardless of the language and tools you're using.
Additionally, Witness's API is compliant with its OpenAPI specification (opens in a new tab), which means tools like OpenAPI Generator (opens in a new tab) can be used to generate client libraries for your language of choice.
There's also an intuitive API explorer (opens in a new tab) page provided for convenience.