matrix-doc/event-schemas/README.md

Testing a schema

There are many JSON Schema validators you can use to validate incoming events. Not all of them support JSON Schema v4, and some of them have bugs which prevent $ref from being resolved correctly. For basic CLI testing, we recommend and have verified they work with the Node.js package z-schema:

 $ npm install -g z-schema
 $ z-schema schema/v1/m.room.message examples/v1/m.room.message_m.text
 schema validation passed
 json #1 validation passed