<!--
name: 'Data: Claude API reference — Ruby'
description: Ruby SDK reference including installation, client initialization, basic requests, streaming, and beta tool runner
ccVersion: 2.1.78
-->
# 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: 16000,
  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: 64000,
  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: 16000,
  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](../shared/tool-use-concepts.md) for the tool definition format and agentic loop pattern.