Code mode is all you need: Why agents writing code > calling tools

10 hours ago

For many agent tasks, the best 'tool' is a small code-execution surface, allowing models to write ordinary code against typed capabilities and enforce security below the model.
Traditional agent toolboxes are growing with many tools, but models already excel at code, which is a more familiar and efficient interface, reducing context usage and tool calls.
Code mode compresses context (e.g., 88% less), reduces token consumption from tool schemas, and allows deterministic logic between calls, such as joins, filters, and error handling.
Models already speak code; custom tools require learning new schemas, while code provides a familiar grammar with types, compilers, error feedback, and concurrency.
Code mode enables browsers to be controlled via JavaScript (e.g., page.evaluate()) instead of needing many interaction tools, making the browser agent more general.
Code mode improves context compression, composition (e.g., controlling browser, querying warehouse, normalizing CSV in one execution), durable artifacts, and self-debugging via compiler feedback.
Agent progression: tool mode (one action at a time) → code mode (whole workflow) → stabilized mode (saved code, code only when environment changes).
The author's internal agent, bb, uses a small core surface with 'exec' for JS execution, making new integrations cheaper by defining typed capabilities once.
Security requires sandbox, credential brokering, capability enforcement, egress control, read/write separation, traces, and retry design; let the model write anything inside the box, then make the box physically incapable of unauthorized actions.
The best agent harnesses pair a few high-consequence tools with a general execution surface, letting agents write code for most tasks.

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Code mode is all you need: Why agents writing code > calling tools