Module messages 

The Messages API.

The headline endpoint of the Anthropic API. Build a request via CreateMessageRequest::builder, then send it through the Messages namespace handle obtained from Client::messages.

Endpoints

Method	Path	Function
POST	/v1/messages	Messages::create (non-streaming)
POST	/v1/messages	Messages::create_stream (SSE)
POST	/v1/messages/count_tokens	Messages::count_tokens

Quick start

use claude_api::{Client, messages::CreateMessageRequest, types::ModelId};
let client = Client::new("sk-ant-...");
let resp = client.messages().create(
    CreateMessageRequest::builder()
        .model(ModelId::SONNET_4_6)
        .max_tokens(256)
        .system("Be concise.")
        .user("What is the capital of France?")
        .build()?,
).await?;

Module layout

• request – CreateMessageRequest, CountTokensRequest, builders
• response – Message, CountTokensResponse, ContainerInfo
• content – ContentBlock / KnownBlock union with forward-compat fallthrough
• stream – StreamEvent, ContentDelta, the EventStream aggregator + on_* callbacks
• tools – Tool, BuiltinTool, CustomTool, ToolChoice
• cache – CacheControl for prompt caching
• thinking – ThinkingConfig for extended thinking
• mcp – McpServerConfig for MCP server invocation
• citation – typed Citation enum
• input – MessageInput, SystemPrompt helpers
• metadata – MessageMetadata, RequestServiceTier

For streaming, see stream for the wire-event types and api::Messages::create_stream for the namespace method.

Re-exports

pub use cache::CacheControl;

pub use citation::Citation;

pub use citation::KnownCitation;

pub use content::CitationConfig;

pub use content::ContentBlock;

pub use content::DocumentSource;

pub use content::ImageSource;

pub use content::KnownBlock;

pub use content::ToolResultContent;

pub use input::MessageContent;

pub use input::MessageInput;

pub use input::SystemPrompt;

pub use mcp::McpServerConfig;

pub use mcp::McpToolConfiguration;

pub use metadata::MessageMetadata;

pub use metadata::RequestServiceTier;

pub use request::CountTokensRequest;

pub use request::CountTokensRequestBuilder;

pub use request::CreateMessageRequest;

pub use request::CreateMessageRequestBuilder;

pub use response::ClearThinkingEdit;

pub use response::ClearToolUsesEdit;

pub use response::ContainerInfo;

pub use response::ContextEdit;

pub use response::CountTokensResponse;

pub use response::KnownContextEdit;

pub use response::KnownStopDetails;

pub use response::Message;

pub use response::RefusalStopDetails;

pub use response::ResponseContextManagement;

pub use response::StopDetails;

pub use stream::ContentDelta;

pub use stream::KnownContentDelta;

pub use stream::KnownStreamEvent;

pub use stream::MessageDelta;

pub use stream::StreamEvent;

pub use thinking::ThinkingConfig;

pub use tools::BuiltinTool;

pub use tools::CustomTool;

pub use tools::KnownBuiltinTool;

pub use tools::Tool;

pub use tools::ToolChoice;

pub use tools::UserLocation;

pub use api::Messages;async

Modules

apiasync

The Messages API namespace.

cache

Cache breakpoints for Anthropic prompt caching.

citation

Typed citations produced by Claude.

content

Content blocks: the building blocks of message bodies and stream deltas.

input

Request-side message structures: MessageInput, MessageContent, SystemPrompt.

mcp

MCP server configuration for the mcp_servers request field.

metadata

Per-request metadata and the request-side service_tier field.

request

Request payloads for the Messages API.

response

Response types returned by the Messages API.

stream

Streaming event types and reconstruction.

thinking

Configuration for extended thinking.

tools

Tool definitions and tool-choice configuration.