---
title: "Design Better Tools for AI Agents"
description: "Make agent tools easier to select, call, validate, and recover from with narrow schemas and actionable errors."
language: en
canonical: https://navinresearch.com/blog/agents/agent-tool-design.md
topics: ["AI agent tool design", "function calling schema", "tool use reliability"]
---

# Design Better Tools for AI Agents

Make agent tools easier to select, call, validate, and recover from with narrow schemas and actionable errors.

**Short answer:** Design tools around user intentions rather than low-level API endpoints. A good tool has a distinct name, a concise description, a strict input schema, a small response, and errors that tell the agent what can be corrected.

## Implementation steps

1. Start from real tasks and list the minimum operations needed to complete them.
2. Use enums, required fields, examples, and server-side validation.
3. Return stable identifiers and compact summaries; store large payloads outside model context.
4. Separate read operations from writes and mark consequential actions clearly.

## Validation checklist

- Measure tool-selection accuracy with confusing neighboring tools.
- Fuzz invalid arguments and ensure no side effect occurs.
- Confirm retries are idempotent or carry an idempotency key.

## Common mistakes

- Exposing every backend endpoint as a tool.
- Descriptions that differ only by one vague verb.
- Returning unbounded logs or documents into context.

## Practical decision

Ship the smallest design that passes the checks above. Record the model, prompt, tool, dataset, and runtime versions used in testing so later changes can be compared rather than guessed. Recheck the linked documentation before relying on provider-specific limits, model names, prices, or preview features; those details change more quickly than the engineering principles in this note.

## Official sources

- [Anthropic, Writing effective tools for agents](https://www.anthropic.com/engineering/writing-tools-for-agents)
- [OpenAI, Function calling guide](https://platform.openai.com/docs/guides/function-calling)

---

Reviewed: 2026-08-24. This concise engineering note is educational, not a claim that Navin Research created or independently verified the cited provider technology.