Claude API — Ruby

Note: The Ruby SDK supports the Claude API. A tool runner is available in beta via `client.beta.messages.tool_runner()`. Agent SDK is not yet available for Ruby.

Installation

```bash gem install anthropic ```

Client Initialization

```ruby require "anthropic"

Default (uses ANTHROPIC_API_KEY env var)

client = Anthropic::Client.new

Explicit API key

client = Anthropic::Client.new(api_key: "your-api-key") ```

Basic Message Request

```ruby message = client.messages.create( model: :"{{OPUS_ID}}", max_tokens: 1024, messages: [ { role: "user", content: "What is the capital of France?" } ] )

content is an array of polymorphic block objects (TextBlock, ThinkingBlock,

ToolUseBlock, ...). .type is a Symbol — compare with :text, not "text".

.text raises NoMethodError on non-TextBlock entries.

message.content.each do |block| puts block.text if block.type == :text end ```

Streaming

```ruby stream = client.messages.stream( model: :"{{OPUS_ID}}", max_tokens: 1024, messages: [{ role: "user", content: "Write a haiku" }] )

stream.text.each { |text| print(text) } ```

Tool Use

The Ruby SDK supports tool use via raw JSON schema definitions and also provides a beta tool runner for automatic tool execution.

Tool Runner (Beta)

```ruby class GetWeatherInput < Anthropic::BaseModel required :location, String, doc: "City and state, e.g. San Francisco, CA" end

class GetWeather < Anthropic::BaseTool doc "Get the current weather for a location"

input_schema GetWeatherInput

def call(input) "The weather in #{input.location} is sunny and 72°F." end end

client.beta.messages.tool_runner( model: :"{{OPUS_ID}}", max_tokens: 1024, tools: [GetWeather.new], messages: [{ role: "user", content: "What's the weather in San Francisco?" }] ).each_message do |message| puts message.content end ```

Manual Loop

See the shared tool use concepts for the tool definition format and agentic loop pattern.

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