How Many Tools Per Agent

When you give an agent a set of tools, the model has to do something subtle on every turn: read all the tool descriptions and pick the right one for the current step.

This is a selection task. The more options you add, the harder that choice becomes. A focused toolset keeps selection sharp; an overloaded one makes the model hesitate, mis-route, or grab the wrong tool.

This lesson answers a deceptively simple question: how many tools should one agent hold?

The practical sweet spot is 4-5 tools per agent. At this size the model can reliably reason about which tool fits each step.

As the count climbs, selection reliability degrades. By around 18+ tools on a single agent, the model starts confusing similar options and choosing poorly. More tools does NOT mean more capability — past a point it means less reliable capability.

• 4-5 tools → optimal selection
• 18+ tools → degraded selection reliability