api-guidelines/evolution/json.md

JSON Format Conventions

Any JSON-based message MUST conform to these rules

• All JSON field names MUST follow the Naming Conventions (snake_case, American English etc.)
• Field names MUST be ASCII alpha num characters, underscore (_) or dollar sign ($)
• Boolean fields MUST NOT be of null value
• Fields with null value SHOULD be omitted
• Empty arrays and objects **SHOULD NOT ** be null (use [] or {} instead)
• Array field names SHOULD be plural (e.g. "orders": [])