---
id: "concept-tool-selection-error"
type: "concept"
source_timestamps: ["00:13:53", "00:14:14"]
tags: ["failure-modes", "tool-use"]
related: ["framework-ai-failure-taxonomy"]
definition: "An AI failure mode where an agent invokes the wrong external tool for a task, usually due to poor tool descriptions or overloaded toolsets."
sources: ["s42-job-market-split"]
sourceVaultSlug: "s42-job-market-split"
originDay: 42
---
# Tool Selection Error

## Definition

A failure mode occurring in agentic systems equipped with external tools (APIs, calculators, search). The agent **incorrectly decides to use a tool that is inappropriate** for the current task, or uses a tool when none was needed.

## Common root causes

- Incorrectly framing the tool's description in the system prompt.
- Providing **too many tools** at once, overloading the agent's routing logic.
- Providing tools whose use cases **overlap**, confusing the agent.

## Countermeasures

- Tighten tool descriptions and disambiguate overlapping tools.
- Limit tool inventory per agent (a function of [[concept-task-decomposition]]).
- Add eval cases that score correct tool selection.

## Position in the taxonomy

Fourth entry in [[framework-ai-failure-taxonomy]].