Not sure if there's really a _standard_, but there are examples of projects[1] and generators[2] that encourage best practices. Presumably if you can document your API as JSON, it should be reasonably well-formed.

[1] https://bgentry.io/blog/2014/01/09/auto-generating-a-go-api-...

[2] https://github.com/pksunkara/alpaca

Update: Here's a link from [1] that may be closer to what you're looking for: http://json-schema.org/