claude-api

Type-safe Rust client for the Anthropic API.

Workspace

Crate	Description
`claude-api`	The SDK
`claude-api-derive`	`#[derive(Tool)]` proc-macro (re-exported via the `derive` feature)
`claude-api-test`	Cassette-based replay + recorder for integration tests

Quick start

[dependencies]
claude-api = "0.5"
tokio = { version = "1", features = ["macros", "rt-multi-thread"] }

use claude_api::{Client, messages::CreateMessageRequest, types::ModelId};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new(std::env::var("ANTHROPIC_API_KEY")?);

    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?;

    for block in &resp.content {
        if let claude_api::messages::ContentBlock::Known(
            claude_api::messages::KnownBlock::Text { text, .. },
        ) = block
        {
            println!("{text}");
        }
    }
    Ok(())
}

See crates/claude-api/examples/ for streaming, streaming-with-callbacks, tool use, derived tools, vision, document, conversation, and the agent loop.

API surface

Every documented Anthropic endpoint is reachable through a typed namespace handle off [Client]:

Namespace	Endpoints	Feature flag
`client.messages()`	create, count_tokens, streaming	(default)
`client.models()`	list, get	(default)
`client.batches()`	create, get, list, cancel, delete, results, wait_for	(default)
`client.files()`	upload, get, list, delete, download	(default)
`client.skills()`	full CRUD across skills + skill versions	`skills`
`client.user_profiles()`	create, list, get, update, create-enrollment-url	`user-profiles`
`client.managed_agents()`	sessions, agents, environments, vaults + credentials, memory_stores + memories + versions, resources, threads, events	`managed-agents-preview`
`client.admin()`	organizations, invites, users, workspaces + members, api_keys, usage_report, cost_report, rate_limits	`admin`

Capabilities

Forward-compatible types. ContentBlock, StreamEvent, ContentDelta, Citation, BuiltinTool, BetaHeader, SessionResource and similar wrapper enums round-trip unknown variants through an Other(Value) arm. New API variants don't break older SDK builds.
Retry-After honored. Configurable RetryPolicy { max_attempts, initial_backoff, max_backoff, jitter, respect_retry_after }.
request-id on every error. Surfaced as Error::request_id() -> Option<&str>.
Streaming with typed EventStream plus optional on_text_delta / on_tool_use_complete / on_thinking_delta / on_message_stop / on_error callback hooks.
Tool dispatch with ToolRegistry, parallel-by-default invocation, mid-stream approval gates, cumulative cost budget, cancellation token.
#[derive(Tool)] proc-macro generates the Tool impl from a struct's JsonSchema (under the derive feature).
Conversation multi-turn helper with cumulative usage and optional context compaction.
PricingTable with bundled per-model rates plus cost_preview() for pre-flight USD estimates.
dry_run mode renders the would-be HTTP request as DryRun { method, url, headers, body } plus to_curl() / to_curl_with_key() helpers.
Auth: API key (default), AWS Bedrock sigv4 signer (bedrock feature), pluggable via the RequestSigner trait.
Sync + async: same surface, blocking variants under the sync feature.
Structured tracing spans + events on every request and retry. Zero plumbing required.
Cassette-based integration tests via claude-api-test -- record once against the real API, replay deterministically in CI.

Feature flags

Flag	Default	Adds
`async`	yes	Async client (tokio + reqwest)
`rustls`	yes	rustls TLS backend
`streaming`	yes	SSE streaming + `EventStream::aggregate` + callback hooks
`sync`		Blocking client (reqwest blocking)
`native-tls`		native-tls instead of rustls
`schemars-tools`		`Tool::from_schemars::<T: JsonSchema>` constructor
`derive`		`#[derive(Tool)]` (pulls in `claude-api-derive`)
`pricing`		`PricingTable` + cost calculation + `cost_preview`
`conversation`		Multi-turn `Conversation` helper
`bedrock`		AWS sigv4 `BedrockSigner`
`vertex`		(placeholder, not yet wired -- see #6)
`admin`		Admin API
`skills`		Skills API
`user-profiles`		User Profiles API
`managed-agents-preview`		Managed Agents preview

Disable defaults if you only want the type definitions:

claude-api = { version = "0.5", default-features = false }

Resources

Examples
Changelog
Open issues -- roadmap items, planned work, known gaps

MSRV

Rust 1.90 or later. Edition 2024.

License

Licensed under either of Apache-2.0 or MIT at your option. Contributions are dual-licensed under the same terms.

claude-api 0.5.3