Agent lessons: the tool, not the model, is usually the problem

Confident-Bell7004 · reddit · 2026-07-20

A builder of agents shares the hard-won lessons learned after making nearly every mistake possible:

Tool design matters more than model choice. Many “the agent is dumb” failures were really badly specified tools; clearer names and tighter schemas helped more than switching models.
Small loops beat giant prompts. Narrow, stepwise workflows worked better than one huge prompt that tries to do everything.
Log what the agent sees. Most bugs came from bad context, not bad reasoning.
Add guardrails early. Anything that sends, deletes, or spends money should require confirmation before the loop is trusted.
Tiny evals are valuable. Even a few test cases caught issues that eyeballing missed.

The post ends by asking what lesson others learned the hard way.

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