Creates a new user message object.

The model will use any available tools.

The model will automatically decide whether to use tools.

The model will use the specified tool.

Provides input and output types that conform to the Anthropic Messages API, as described in the [API Reference] docs.

The input object for the Anthropic Messages API.

The output object for the Anthropic Messages API.

A tool object that the model may call.

Content may be either a single string or an array of content blocks, where each block has a specific type.