Wrap a Smaller Agent as a Tool for a Bigger One

Problem/Feature Description

A developer is building a coding agent. The main agent edits files, runs tests, and opens PRs — it's expensive (Opus-class model, many tools). They've also built a smaller, cheaper agent whose only job is to find references to a symbol across a large codebase — it uses a Haiku-class model and just a couple of grep-style tools. They've already constructed both agents independently and both work on their own.

They want the main agent to be able to "ask the find agent" — that is, to invoke the find agent as if it were a single tool call, getting back the search result, then continue its work. They emphasize they don't want to inline the find logic into the main agent; the find agent should stay separate (different model, different system prompt, different tool set) for cost reasons.

Output Specification

Walk through how to make the find agent callable from the main agent. Produce the modified source for the main agent's construction in a single response.