Creates a Claude message response for text, multimodal input, and tool use.
Use this section for Claude-native message payloads, multi-turn context, multimodal input, and tool calling.
x-api-key and anthropic-versionsystem is a top-level field rather than a message inside messages[]messages[].content uses content blocks and should not be flattened too earlytools, and later turns must send back tool_result blocksAnthropic API version header.
"2023-06-01"