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

Annotations already flag destructive=true, non-idempotent and open-world, but the description goes well beyond them: it discloses that the saved trip is mutated, that the change is reversible because the previous choice can be re-selected the same way, and that nothing is booked or paid. It also notes the whole trip is re-priced, matching website 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?

Three sentences, each doing distinct work: action and re-pricing, return payload, then side effects and reversibility. The destructive consequence is stated plainly and no sentence is padding.

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 no output schema, the description usefully specifies the return value (updated option plus Safe Trip Total before and after) and covers mutation, reversibility and the absence of booking/payment. The only shortfall is not explaining how to source lineId and optionId, which matters for a four-required-parameter mutation.

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?

Schema coverage is only 25%, with just 'choice' documented in the schema; the description reinforces that it is a 1-10 numbered choice from trip_alternatives. The other three identifiers (tripId, optionId, lineId) remain unexplained, though 'one line of an option' gives a weak hint about the hierarchy. It partially compensates but leaves a real gap for a 4-parameter tool.

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?

States a specific verb (replaces), a specific resource (one line of an option within a trip), and the re-pricing consequence, all in the first sentence. It also names the sibling tool trip_alternatives as the origin of the numbered choice, which lets an agent separate it from plan_trip and get_trip without opening any schema.

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 makes the workflow prerequisite clear: the 'choice' must be a numbered option from trip_alternatives, implying that tool should be called first. It stops short of explicit when-not guidance or stating that get_trip is the way to obtain lineId/optionId, so it is clear context rather than full routing.

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