[axeldunkel]

Good question on Code Mode internals.

In Code Mode the model sees only two tools by default: list_tools(pattern) and execute_code(code). list_tools takes a regex and returns TypeScript signatures for matching tools. execute_code runs JavaScript that calls them.

So when the model actually needs the GitHub API for example, it calls list_tools("github.*pull") - it gets back just the typed signatures for those endpoints, and then writes code against them. Your second hypothesis is the mechanism: a meta-tool that queries on demand. The typed signatures (first hypothesis) are what the model reasons over once it has them.

That is what really brings the cost down. A large API as MCP tool definitions is easily 40-50k tokens upfront. The same API via list_tools + execute_code is ~1k for the two tool descriptions, plus only the signatures the model pulls per query.