A single message in multi-message mode.
{ "$schema": "https://json-schema.org/draft/2020-12/schema", "$id": "#/components/schemas/MessageItem", "title": "MessageItem", "type": "object", "description": "A single message in multi-message mode.", "required": [ "payload" ], "properties": { "payload": { "type": "string", "description": "The message content. May be plain text, JSON, or XML encoded as a string." }, "properties": { "type": "object", "description": "Optional custom metadata key-value pairs associated with this message.", "additionalProperties": { "type": "string" } } } }