Crate claude_api 

Type-safe Rust client for the Anthropic API.

Every documented Anthropic endpoint is reachable through a typed namespace handle off Client. Forward-compatible by design – unknown content blocks, stream events, citations, and similar discriminated unions round-trip through Other(Value) arms so new server-side variants don’t break older SDK builds.

Quick start

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

let client = Client::new(std::env::var("ANTHROPIC_API_KEY").unwrap());

let resp = client
    .messages()
    .create(
        CreateMessageRequest::builder()
            .model(ModelId::SONNET_4_6)
            .max_tokens(256)
            .user("Hello!")
            .build()?,
    )
    .await?;

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

Module map

Endpoints are organized by Anthropic resource. Each namespace handle is reached via a method on Client:

Module	Namespace	Default?
messages	client.messages()	yes
models	client.models()	yes
batches	client.batches()	yes
files	client.files()	yes
skills	client.skills()	feature skills
user_profiles	client.user_profiles()	feature user-profiles
managed_agents	client.managed_agents()	feature managed-agents-preview
admin	client.admin()	feature admin

Cross-cutting machinery:

Module	Purpose
auth	API-key wrapper + auth::RequestSigner trait
bedrock	AWS sigv4 bedrock::BedrockSigner (feature bedrock)
vertex	GCP OAuth2 vertex::VertexSigner (feature vertex)
beta	BetaHeader open-string enum for the anthropic-beta header
retry	retry::RetryPolicy honoring Retry-After
error	Error with request_id, retry classification
pagination	Paginated and PaginatedNextPage
types	Shared primitives: ModelId, Role, Usage, StopReason
conversation	Multi-turn helper with cumulative usage (feature conversation)
tool_dispatch	ToolRegistry, agent loop, parallel dispatch, approval gates
pricing	PricingTable (feature pricing)
cost_preview	Pre-flight USD estimates (features async + pricing)
dry_run	Render the would-be HTTP request without sending
sse	SSE wrapper used by streaming endpoints (feature streaming)

Forward compatibility

Every wire-level discriminated union has an Other arm:

• messages::ContentBlock – text / image / tool_use / thinking / … / Other(Value)
• messages::KnownBlock – the typed variants
• messages::stream::StreamEvent – SSE events
• messages::citation::Citation – citation kinds
• BetaHeader – known beta header values + Other(String)

When Anthropic adds a new variant, your code that pattern-matches on Known(...) continues to compile; the new variant lands in Other(...) until you upgrade. See the upgrade contract in the README before bumping past a release that promotes an Other to Known.

Error handling

All endpoint methods return Result<T> where Error carries:

• HTTP status (when the API responded)
• request-id (always populated when the server sent one)
• Retry classification (is_retryable()) and parsed Retry-After (retry_after())
• Structured kind (error::ApiErrorKind) for known error types

The retry::RetryPolicy applied by the client respects Retry-After by default and uses jittered exponential backoff otherwise. Disable retries with RetryPolicy::none() if your caller wraps its own retry logic.

Observability

Every HTTP request emits a tracing span at debug level with method, path, and request_id fields. Retries log at warn with attempt, retry_in_ms, and status. No env-var gating is required; install a tracing-subscriber to capture the events.

Re-exports

pub use beta::BetaHeader;

pub use client::Client;async

pub use client::ClientBuilder;async

pub use error::Error;

pub use error::Result;

Modules

adminadmin

Anthropic Admin API.

auth

Authentication primitives and the RequestSigner hook.

batches

The Batches API: submit a batch of message requests, poll for completion, stream per-request results.

bedrockbedrock

AWS Bedrock support: a RequestSigner that signs HTTP requests with sigv4.

beta

Typed anthropic-beta header values.

blockingsync

Blocking (synchronous) variants of the HTTP surface.

clientasync

HTTP client and builder.

conversationconversation

Multi-turn conversation helper.

cost_previewasync and pricing

CostPreview – estimate the USD cost of a request before sending it.

derivederive

Procedural-macro re-exports for the derive feature.

dry_runasync

DryRun – preview the HTTP request that would be sent, without firing it.

error

Error type, result alias, and wire-format error payload.

files

The Files API (beta).

managed_agentsmanaged-agents-preview

Anthropic Managed Agents API (preview).

messages

The Messages API.

models

The Models API.

pagination

Generic pagination wrapper used across paginated endpoints.

pricingpricing

Per-model pricing and cost calculation.

retryasync or sync

Retry policy honoring Retry-After.

skillsskills

The Skills API (beta).

ssestreaming

Low-level Server-Sent Events parsing.

tool_dispatchasync

Tool-dispatch: the Tool trait, registry, typed inputs, and the agent loop runner.

types

Foundational shared types used across every API resource.

user_profilesuser-profiles

The User Profiles API (beta).

vertexvertex

Google Cloud Vertex AI support: a RequestSigner that attaches an OAuth2 bearer token so requests are authenticated against the Vertex AI Anthropic endpoint.