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::ContainerInfo;

pub use response::CountTokensResponse;

pub use response::Message;

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 namespace: Messages::create, Messages::count_tokens, and their _with_beta siblings.

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: Message, CountTokensResponse, ContainerInfo.

stream

Streaming event types and reconstruction.

thinking

Configuration for extended thinking.

tools

Tool definitions and tool-choice configuration.