Primary part of message in text.
OptionalidOptional stable identifier for deduplication or threading.
Author of the message.
OptionalsignatureOptional signature for the thinking field.
This is only applicable to certain LLM APIs that require a signature as part of the thinking payload.
OptionalthinkingInternal “thinking” text used by some models before producing final output.
Optionaltool_Tool-call parts emitted alongside the main contents.
A simplified form of [Message] for concise definition. All other members are identical to [Message], but
contentsis aStringinstead ofVec<Part>. This can be converted to Message via.into().