# Tool Explosion

> Exposing every available tool to the agent on every request — and watching function-calling accuracy collapse past ~20 tools.

- **Category**: Agentic AI
- **Subcategory**: Anti-Patterns
- **Canonical URL**: https://designpattern.fyi/patterns/tool_explosion/

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## Description
**Intent**: Defaulting to "expose all tools" because registration is cheap — then discovering that selection accuracy drops measurably as the tool list grows.

**Context**: MCP servers, plugin ecosystems, and tool registries make it trivial to expose dozens or hundreds of tools. Teams expose everything "so the agent can reach for anything." Past ~20 tools, function-calling accuracy measurably degrades — and the token cost of carrying large tool definitions in every prompt compounds the problem.

**Solution**: Use a tool-loadout: curate the relevant subset per task type. Cap exposed tools at a tested threshold. Measure function-calling accuracy as a release gate.



## Use Cases
- Never use this; past about 20 tools, function-calling accuracy drops sharply.
- Use tool-loadout to select per-task subsets and cap exposed tools at a tested threshold.
- Measure function-calling accuracy as a release gate.






## Trade-offs




### Considerations & Drawbacks

- Selection accuracy degrades — the model picks the wrong tool or hallucinates one

- Token cost rises from large tool definitions carried in every prompt

- Cache misses on every tool list change, adding latency







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**Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/tool-explosion/)