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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, so the bar is lower, but the description adds the crucial preview/confirm gate and the fact that a confirmation_token is returned and must be echoed back with unchanged parameters. It does not explain what happens to the underlying reservation if the company declines or what a failed confirmation costs the user, leaving the destructive profile partly unqualified.

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 prerequisite and two-phase contract are front-loaded in the first two sentences, with the example placed last where it belongs. The inline JSON example is slightly dense but earns its space by showing which fields travel together on the confirm call.

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?

With an output schema present, the description need not explain return values, yet it still flags confirmation_token and the 'decision' field. For a destructive, open-world mutation with 6 params, the main remaining gap is the absence of any statement about denial handling or what market/reservation_number are for.

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?

At 50% schema coverage the description must compensate, and it does for the highest-risk fields: confirm is framed as preview-vs-execute, confirmation_token is tied to the preview step, and new_return_at must be identical between calls. market and reservation_number are never mentioned, and management_id is only covered indirectly ('from_verify' in the example vs. the schema's verify_reservation_management), so the coverage is good but incomplete.

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 positions the tool relative to quote_extension ('Use after quote_extension when the user asked to extend') and makes clear it submits an extension request that 'the rental company decides', which cleanly separates it from the quoting sibling. The specific action verb is implied by the sequencing rather than stated outright, keeping it just short of a 5.

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?

It names the prerequisite sibling (quote_extension) and the triggering condition ('when the user asked to extend'), then prescribes an explicit two-step protocol: preview first without confirm, then re-call with confirm=true plus token and identical new_return_at after 'the user's explicit yes'. This is exactly the when/when-not guidance an agent needs.

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