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

Annotations already mark the tool as read-only, idempotent, and non-destructive, and the description reinforces and extends this by disclosing the exact result shape: one entry per partner, only verified pickup facts, a tracked booking link, and an empty list when no partner covers the city. This adds meaningful behavior beyond the annotations with no contradiction.

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?

One well-paced sentence that front-loads the core purpose, then adds output semantics and the empty-list case. There is no filler, repetition of schema details, or wasted words.

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 an output schema already exists, the description does not need to enumerate return fields. It covers the selection rationale, result shape, and empty-case behavior, while the required parameters are fully documented in the schema.

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?

Both parameters are fully described in the input schema with 100% coverage, so the description does not need to explain country/city semantics. The description adds little beyond the word 'city' and correctly does not duplicate schema details.

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 states a specific resource ('Car hire partners that verifiably cover a city') and a concrete output: one entry per partner with checked pickup facts and a tracked booking link. The read-only qualifier and empty-list behavior clearly distinguish it from sibling travel tools.

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?

The description implies when to call this tool (when the agent needs car hire coverage for a city), but it does not explicitly state when to use it versus alternatives like search_places or stays. There are no exclusions or named sibling conditions.

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