Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world behavior, so the description only needs to add context beyond that. It does add useful scope boundaries (no live fares, no booking) and mentions the car-hire sister tool, but it does not disclose anything about the response shape or invocation behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single efficient sentence that front-loads the main coverage areas. It is appropriately sized for a simple capability-overview tool, though the list-like construction could be slightly clearer.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has no parameters, rich annotations, and an output schema, the description supplies enough context: what topics are covered, what is out of scope, and a pointer to a related tool. It does not need to explain return values because the output schema handles that.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so parameter semantics fall to the baseline of 4. The description appropriately does not waste space discussing inputs.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly indicates this is an overview of Airfare Brain's coverage: airlines, fee research, limitations, and a related car-hire tool. It distinguishes itself from data-query siblings by being meta-informational and by explicitly naming what the suite does NOT do. However, it never states outright 'returns capability information,' leaving the verb implicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied—call this to learn coverage and limitations before using specific tools—but there is no explicit 'use this when' or 'use X instead' guidance. The mention of a sister car-hire tool hints at alternatives, yet the siblings listed (airline_fees, list_airlines, true_cost) are not directly addressed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.