CookiesForAI

claude-api

Claude API

Claude API is Anthropic's open-source agent skill for code that calls Claude: current model IDs and prices, guides for seven SDK languages plus cURL, and guided migrations to newer models.

Agent skill by Anthropic Official · Updated

Install Claude API

In Claude Code, add Anthropic's skills marketplace

Terminal
/plugin marketplace add anthropics/skills

Then install the claude-api plugin

Terminal
/plugin install claude-api@anthropic-agent-skills

Or install only this skill, for any agent, with the skills CLI

Terminal
npx skills add anthropics/skills --skill claude-api

Or paste this into your coding agent: Install the agent skill claude-api from github.com/anthropics/skills. A skill can include scripts that run on your computer, so read its source first.

What Claude API does

Claude API is Anthropic's reference skill for building applications on Claude. It loads when a prompt names Claude, Anthropic or a Claude model, when you ask about model choice, pricing or limits, or when a task is LLM-shaped and no provider is named. It skips projects that use another provider such as OpenAI or Gemini, and it will not add Anthropic SDK calls to a file written for one.

With Claude API loaded, the agent detects the project language (Python, TypeScript, Java, Go, Ruby, C#, PHP or cURL) and reads that language's bundled guides. It uses the official Anthropic SDK, uses raw HTTP only when asked, and takes function names from documentation instead of guessing. The skill carries a dated table of model IDs with prices, a table of API shapes that changed in 2025 and 2026, and quick references for thinking, caching, streaming, tool use and Managed Agents.

The Claude API skill also runs named workflows through /claude-api subcommands: migrate (move code to a newer model), upgrade (the Python SDK from 0.x to 1.x), prompt-audit (find dated patterns in prompts and CLAUDE.md files), cost-optimize, build-eval, hillclimb (improve an app against an eval), preserved-thinking-migration and managed-agents-onboard. The cost and eval workflows ask for your approval before they spend money on model calls.

When to use Claude API

  • You are adding a Claude call to an app and want current model IDs and SDK code, not patterns from old training data.
  • You need to move existing code to a newer Claude model.
  • Your Claude API bill is high and you want the agent to look for savings such as caching and batching.
  • You are choosing between a single API call, tool use and Managed Agents for an agent you are building.

When to pick something else

  • Your project calls OpenAI, Gemini or another provider: the skill stands down when it finds one.
  • You want to give an agent tools through MCP rather than call the API: use MCP Builder.

Which agents Claude API works in

Anthropic documents Claude API for Claude Code, Claude API. The open skills CLI also installs it into 78 agents, including Claude Code, Codex, Cursor, Gemini CLI, GitHub Copilot, OpenCode (we listed it with the CLI on October 1, 2026). See where each agent looks for skills.

Its named workflows start as /claude-api <subcommand>, the slash command form Claude Code gives skills; the SKILL.md also accepts the bare subcommand as the request, which works in agents without slash commands. It asks for your language with Claude Code's AskUserQuestion tool and falls back to Python where that tool is missing.

Claude API license

Claude API is published under Apache-2.0. Apache-2.0 comes from the LICENSE.txt in the skill's own folder (read 2026-10-01); the anthropics/skills repository has no root license file. In practice you may use, change and share the skill in any agent, commercially too, as long as you keep the license text and notices and mark your changes.

  • React Best Practices: React Best Practices is Vercel Engineering's agent skill of 70 performance rules for React and Next.js, ranked by impact, which the agent applies when it writes or reviews code. (31,813 repository stars on October 2, 2026)
  • React Composition Patterns: React Composition Patterns is Vercel's agent skill for React component APIs: compound components, lifted state and explicit variants instead of a growing list of boolean props. (31,813 repository stars on October 2, 2026)
  • React Native: React Native is Vercel's agent skill of React Native and Expo rules, ranked by impact: list performance, animations, native navigation and UI patterns for faster mobile apps. (31,813 repository stars on October 2, 2026)
  • React View Transitions: React View Transitions is Vercel's agent skill for animating route changes, shared elements and list reorders with React's ViewTransition component, in Next.js and other React apps. (31,813 repository stars on October 2, 2026)

More from Anthropic

  • Academy Guide: Academy Guide is Anthropic's agent skill that ends Claude's answers about using Claude with one or two matching Claude Academy courses or tutorials, and only when the match is strong. (179,326 repository stars on October 2, 2026)
  • Algorithmic Art: Algorithmic Art is Anthropic's open-source agent skill for generative art: the agent writes a short art philosophy, then builds an interactive p5.js piece with seeds and parameter sliders. (179,326 repository stars on October 2, 2026)
  • Brand Guidelines: Brand Guidelines is Anthropic's open-source agent skill that holds Anthropic's own brand colors and fonts, so an agent can give a document, slide deck or web artifact the Anthropic look. (179,326 repository stars on October 2, 2026)
  • Canvas Design: Canvas Design is Anthropic's open-source agent skill for static visual work: the agent writes a design philosophy, then makes a poster or art piece as a finished PNG or PDF file. (179,326 repository stars on October 2, 2026)

Lists that include claude-api