ChatMessage schema

Field	Type and description
`role` Required	string The role of the message author. Allowed values: `["system","user","assistant","tool"]`
`content` Required	schema The message content (text or multimodal content parts). Assistant tool-call messages may contain content: null. oneOf string array of object Array items object null
`reasoning_content`	string \| null The model's reasoning trace when the model produces one; null otherwise. Populated by some reasoning models only — a consumer must not assume it carries content. Reasoning that a model writes inside `content` between <think> or <thinking> tags is moved here, with or without streaming.
`name`	string Optional name for the participant.
`tool_calls`	array of object Tool calls generated by the assistant. Array items object
`tool_call_id`	string ID of the tool call this message responds to.