Introduction

Building applications with Claude’s API is powerful, but keeping up with SDK updates, model migrations, and best practices can be overwhelming. Enter the Claude API Skill — an open-source Agent Skill that equips Claude with detailed, up-to-date reference material for two primary Anthropic surfaces: the Messages API and Claude Managed Agents (beta).

This guide walks you through what the skill provides, how it activates, and how to use it effectively in your projects. Whether you’re a seasoned developer or just starting with Claude, this skill will save you time and reduce context waste.

What Is the Claude API Skill?

The Claude API Skill is a pre-built Agent Skill that lives in the Anthropic skills repository. It’s bundled with Claude Code and can be installed in any environment that supports Agent Skills. Its core purpose: give Claude the latest, most relevant documentation for your specific task without loading everything at once.

Supported Surfaces

• Messages API — The primary surface for single requests, streaming chat, tool use, batch processing, prompt caching, structured outputs, and custom agent loops.
• Claude Managed Agents (beta) — A first-party surface for server-managed stateful agents with Anthropic-hosted tool execution, persistent agent configs, and per-session containers.

Language Coverage

The skill covers 8 programming languages for the Messages API:

• Python, TypeScript, Java, Go, Ruby, C#, PHP, and cURL

For Managed Agents, it covers 7 languages (C# is not currently supported):

• Python, TypeScript, Java, Go, Ruby, PHP, and cURL

How Progressive Disclosure Works

One of the skill’s smartest features is progressive disclosure. Instead of dumping all documentation into the context window, Claude loads only the documentation relevant to:

• Your project’s language
• The surface you’re using (Messages API or Managed Agents)
• The specific task (tool use, streaming, batch processing, etc.)

This keeps context efficient, reduces token waste, and improves response accuracy.

What the Skill Provides

For the Messages API

When triggered, the skill equips Claude with:

• Language-specific SDK documentation: Installation, quick start, common patterns, and error handling for your project’s language.
• Tool use guidance: Language-specific examples and conceptual foundations for function calling, including the beta tool runner where available.
• Streaming patterns: Implementation details for building chat UIs and handling incremental display.
• Batch processing: Offline batch processing at 50% cost.
• Prompt caching: Prefix-stability design, breakpoint placement, and silent-invalidator audit.
• Model migration: Step-by-step guidance for migrating to newer Claude models (including breaking changes on Claude Opus 4.7).
• Current model information: Model IDs, context window sizes, and pricing.
• Common pitfalls: Detailed guidance on avoiding frequent mistakes when integrating with the API.

For Managed Agents (beta)

The skill also provides:

• Onboarding flow: An interview-driven walkthrough for setting up a new Managed Agent from scratch, available via the /claude-api managed-agents-onboard subcommand.
• Language-specific Managed Agents docs: Creating persistent agents, starting sessions, streaming events, and handling tool confirmations.
• Client patterns: Lossless stream reconnect, processed_at queued/processed gate, interrupt handling, file-mount gotchas, and credential handling.
• Deployment constraints: Managed Agents is first-party only (not available on Amazon Bedrock, Google Vertex AI, or Microsoft Foundry) — the skill routes third-party deployments to Messages API + tool use instead.

When the Skill Activates

The skill activates automatically in these scenarios:

• Your code imports an Anthropic SDK (anthropic for Python, @anthropic-ai/sdk for TypeScript/JavaScript)
• You ask Claude to help build, debug, or optimize something with the Claude API, an Anthropic SDK, or Managed Agents
• You add, modify, or tune a Claude feature in a file (prompt caching, tool use, streaming, etc.)

You can also trigger it manually by asking Claude a question like:

"Use the Claude API skill to show me how to set up streaming with Python."

Practical Code Examples

Example 1: Streaming with the Messages API (Python)

import anthropic
client = anthropic.Anthropic()
with client.messages.stream(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Tell me a short story."}]
) as stream:
    for text in stream.text_stream:
        print(text, end="", flush=True)

Example 2: Tool Use with TypeScript

import Anthropic from '@anthropic-ai/sdk';
const anthropic = new Anthropic();
const response = await anthropic.messages.create({
  model: 'claude-sonnet-4-20250514',
  max_tokens: 1024,
  tools: [{
    name: 'get_weather',
    description: 'Get the current weather for a location',
    input_schema: {
      type: 'object',
      properties: {
        location: { type: 'string' }
      },
      required: ['location']
    }
  }],
  messages: [{ role: 'user', content: 'What\'s the weather in Tokyo?' }]
});
console.log(response.content);

Example 3: Batch Processing (Python)

import anthropic
client = anthropic.Anthropic()
Create a batch of messages
batch = client.batches.create(
    requests=[
        {
            "custom_id": "request-1",
            "params": {
                "model": "claude-sonnet-4-20250514",
                "max_tokens": 100,
                "messages": [{"role": "user", "content": "What is 2+2?"}]
            }
        },
        {
            "custom_id": "request-2",
            "params": {
                "model": "claude-sonnet-4-20250514",
                "max_tokens": 100,
                "messages": [{"role": "user", "content": "What is the capital of France?"}]
            }
        }
    ]
)
print(f"Batch created: {batch.id}")

Best Practices for Using the Skill

• Let it activate naturally: The skill triggers automatically when you import an SDK or ask API-related questions. Don’t force it unless you need a specific subcommand.
• Use the /claude-api subcommands: For Managed Agents onboarding, use /claude-api managed-agents-onboard to get an interview-driven setup.
• Combine with other skills: The skill works well alongside other Agent Skills like the Memory tool or Web search tool for richer workflows.
• Keep context lean: Because the skill uses progressive disclosure, you can ask complex multi-step questions without blowing up your context window.

Key Takeaways

• The Claude API Skill provides up-to-date, language-specific documentation for both the Messages API and Managed Agents, reducing the need to memorize SDK details.
• Progressive disclosure keeps context efficient by loading only the documentation relevant to your project’s language, surface, and task.
• The skill activates automatically when you import an Anthropic SDK or ask API-related questions, but you can also trigger it manually.
• It covers 8 languages for the Messages API and 7 for Managed Agents, with practical examples for tool use, streaming, batch processing, and more.
• Use the skill to avoid common pitfalls, migrate models smoothly, and build production-ready applications faster.