The Complete Claude API Learning Hub
Everything you need to build with Claude — from your first API key to production-ready AI agents. Free, in-depth guides with Python and JavaScript code examples.
What is the Claude API?
The Claude API is Anthropic's REST API that gives developers programmatic access to Claude — a family of AI models capable of reasoning, writing, coding, analysing documents, and using tools. Using the API, you can embed Claude's intelligence into your own applications: chatbots, coding assistants, data pipelines, and autonomous agents. The API uses a simple messages-based interface and supports Python and JavaScript SDKs.
First time here?
Get your API key and make your first API call in under 10 minutes.
Get your API keyBuilding an agent?
Learn how Claude reasons, uses tools, and operates in agentic loops.
Explore agentsCutting API costs?
Prompt caching can cut your API bill by up to 90% on repeated context.
Learn prompt cachingGetting Started
Everything you need before writing your first API call — account setup, API keys, model selection, and your first working request.
Core API Features
The Messages API, structured outputs, vision, file uploads, streaming, prompt caching, and extended thinking — the building blocks of any Claude application.
Prompt Engineering
Write prompts that reliably produce high-quality outputs — from beginner fundamentals to advanced techniques like chain-of-thought and few-shot learning.
Tool Use & Agents
Give Claude the ability to call functions, search the web, use computers, and operate in agentic loops — the frontier of AI-powered applications.
Build Real Projects
End-to-end project tutorials — build production-ready AI apps with the Claude API, from chatbots to coding agents.
Test Your Knowledge
Quizzes and knowledge tests to verify your understanding of the Claude API and Anthropic ecosystem.
Why Build with the Claude API?
Claude is designed from the ground up for reliability in production. Unlike consumer AI products, the Claude API gives you precise control over system prompts, conversation history, output format, and model selection. The Claude model family — Opus, Sonnet, and Haiku — spans the full spectrum from maximum capability to minimum latency, so you can match the model to the task rather than overpaying for every request.
Cost is a first-class concern when building AI products. The Prompt Caching guide shows how to cache large, repetitive system prompts and documents to cut API costs by up to 90%. The API Pricing guide breaks down input vs output token costs, batch pricing, and how to estimate costs before you build.
From Simple Completions to Full Agents
The Claude API supports a spectrum of integration depths. At the simplest level, you send a message and receive a reply — useful for text generation, summarisation, and classification. The next level adds tool use, where Claude can call your functions to look up data, write files, or trigger actions in external systems. At the most advanced level, Claude operates in an agentic loop — reasoning about a goal, selecting tools, executing actions, evaluating results, and iterating until the task is complete.
The Model Context Protocol (MCP) extends this further by providing a standardised way for Claude to connect to any external tool or data source — databases, APIs, file systems, and more — without custom integration code per tool.
Learning Path: From Zero to Production
If you are starting from scratch, the recommended path is: (1) get your API key and set up the Console, (2) make your first API call in Python or JavaScript, (3) understand the Messages API structure — roles, turns, and system prompts, (4) add prompt engineering to improve output quality, (5) extend with tool use to connect Claude to real data, then (6) build a complete project from the Build Real Projects cluster above. The knowledge quizzes at the end of each cluster let you verify your understanding before moving on.
Claude API vs Claude.ai
Claude.ai is Anthropic's consumer product — a browser-based chat interface aimed at end users. The Claude API is the developer-facing product — a REST API that lets you integrate Claude into your own software. They share the same underlying models, but the API gives you control over every parameter: system prompts, conversation context, output format, tool definitions, and model version pinning. If you are building a product rather than using Claude yourself, the API is what you need.