MechanismArticle

OpenAI's new Programmatic Tool Calling feature lets GPT-5.6 models compose and run JavaScript that orchestrates tool calls, which could help bridge the gap between MCP-style tool use and full terminal sessions composing CLI utilities.

GPT-5.6 adds Programmatic Tool Calling, letting the model generate and execute JavaScript to orchestrate tool calls, a mechanism the author compares to Anthropic's code-execution-enabled web search tool. ✦ AI generated

Simon Willison · Simon Willison's Weblog · 2026-07-09 · original ↗

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Programmatic Tool Calling allows the models to "compose and run JavaScript that orchestrates tool calls" - which sounds to me like it could help bridge the gap between MCPs and full terminal sessions that can compose CLI utilities in useful ways. Also reminiscent of the dynamic filtering mechanism Anthropic added to their web search tool, which allows code execution against web results as part of a single model turn.

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▦ Anthropic ▦ OpenAI ✳ Programmatic Tool Calling

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