Introducing advanced tool use on the Claude Developer Platform \ Anthropic
The Tool Search Tool lets Claude dynamically discover tools instead of loading all definitions upfront. You provide all your tool definitions to the API, but mark tools with defer_loading: true to make them discoverable on-demand. Deferred tools aren't loaded into Claude's context initially. Claude only sees the Tool Search Tool itself plus any tools with defer_loading: false (your most critical, frequently-used tools).
With Programmatic Tool Calling:
Instead of each tool result returning to Claude, Claude writes a Python script that orchestrates the entire workflow. The script runs in the Code Execution tool (a sandboxed environment), pausing when it needs results from your tools. When you return tool results via the API, they're processed by the script rather than consumed by the model. The script continues executing, and Claude only sees the final output.