Claude API Skill - API Reference Guidance for Claude

Source: Content adapted from anthropics/skills (MIT). Last synced July 8, 2026, against the July 1, 2026 upstream update - this is one of the most actively maintained official skills.

Overview

The claude-api skill is Anthropic's answer to a hard problem: models' training knowledge of their own API goes stale. It keeps current model IDs, pricing, and SDK patterns at Claude's fingertips - the SKILL.md literally contains a section titled "⚠️ API Drift - Your Training Prior May Be Stale" and a model table cached with an explicit date.

How the skill works

The SKILL.md (roughly 73 KB - by far the largest official skill) is structured as a reference router:

• Before you start / defaults - output requirements and safe defaults
• Which surface should I use? - a decision tree across the Messages API, Tool Runner, Managed Agents, and the Agent SDK, including "Should I build an agent?"
• Current models - a dated table (cached June 24, 2026 as of this sync) covering the Claude 5 family including Fable 5, with IDs and capabilities
• Authentication quick reference plus language detection and per-language feature support

Beyond the SKILL.md, the folder fans out into per-language reference packs: curl, Python, TypeScript, Go, C#, and more - each with files like streaming.md, tool-use.md, batches.md, files-api.md, and managed-agents.md.

What's inside the skill folder

• SKILL.md - the router and model reference
• curl/, csharp/claude-api/, go/, and other per-language directories with focused reference files
• LICENSE.txt

Key takeaways for your own skills

• Date-stamp cached facts ("Current models, cached 2026-06-24") so both Claude and readers know freshness at a glance.
• The router + per-language-files layout shows how to keep a huge knowledge skill loadable: the main file decides, the leaf files carry detail.

See it on GitHub

skills/claude-api