Mid-conversation system messages and tool changes

First steps

Intro to ClaudeGet your API keyQuickstartAuthentication

Building with Claude

Features overviewUsing the Messages APIStop reasons and fallbackRefusals and fallbackFallback credit

Model capabilities

EffortTask budgets (beta)Fast mode (research preview)Structured outputsCitationsStreaming MessagesBatch processingSearch resultsStreaming refusalsMultilingual supportEmbeddings

Tools

OverviewHow tool use worksTutorial: Build a tool-using agentDefine toolsHandle tool callsParallel tool useTool Runner (SDK)Strict tool useServer toolsWeb search toolWeb fetch toolCode execution toolAdvisor toolTool search toolMemory toolBash toolText editor toolComputer use toolTroubleshooting

Tool infrastructure

Tool referenceManage tool contextTool combinationsTool use with prompt cachingProgrammatic tool callingFine-grained tool streaming

Context management

Context windowsCompactionContext editingPrompt cachingMid-conversation system messages and tool changesBuild an orchestration modeCache diagnostics (beta)Token counting

Working with files

Files APIPDF support

Skills

OverviewQuickstartBest practicesSkills for enterpriseSkills in the API

MCP

Remote MCP serversMCP connector

Claude on cloud platforms

Amazon Bedrock (Opus 4.7 and later)Amazon Bedrock (Opus 4.6 and earlier)Claude Platform on AWSGoogle CloudMicrosoft Foundry