httpbin.org : A simple HTTP Request & Response Service.
Anything to Triples : Anything To Triples (any23) is a library, a web service and a command line tool that extracts structured data in RDF format from a variety of Web docu...
Plasticity : Extract entities, relationships, and context from text using the Sapien Language Engine. This general natural language understanding API is used for t...
Freebase : A community-curated database of well-known people, places, and things
JSON Schema : JSON Schema is a vocabulary that allows you to annotate and validate JSON documents.
Bluepine is a DSL for defining API Schema/Endpoint with the capabilities to generate Open API (v3) spec, validate API request and serialize object for API response based on single schema definition.