What it is
The Claude Platform, formerly the Anthropic API, is how developers build on Claude models: Fable 5.1 for multi-day autonomous work, Opus 5.5 and Sonnet 5.5 for coding and agents, and Haiku 5.5 for fast, low-cost tasks. The Messages API supports tool use, structured outputs, code execution, computer use, web search and fetch, and context windows up to 1 million tokens. Claude Managed Agents (beta) adds hosted agent infrastructure, and the Claude Console handles keys, usage and workspaces.
Billing is per million tokens, from $0.10 input for Haiku 5.5 up to $10 input and $50 output for Fable 5.1. Batch processing cuts costs by 50% and prompt caching by up to 90%. API usage is billed separately from Claude chat subscriptions.
Best for
- Building coding agents and long-running autonomous agents
- Apps that need a context window up to 1 million tokens
- Teams that also want Claude through AWS, Google Cloud or Microsoft Foundry