Anthropic Claude Tool Use(2024年5月-)。tools array定義(name/description/input_schema JSON Schema)・Claude tool_use stop_reason・tool_use_id+result return・Forced tool use(tool_choice: {type: tool, name: ...})・Auto tool choice・None choice・Parallel tool calls(multi-tool simultaneous・Opus 4.7 native)・Multi-step tool use loop(agent loop)・OpenAI Function Calling同等・Tool definitions in cache(prompt_cache対応)・Computer Use Tools(bash, str_replace_editor, computer)・Anthropic Cookbook examples・2026年 Tool Use + MCP統合 Agent定番。