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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description goes further by disclosing value-validation behavior that annotations cannot express: exact character-for-character matching, expiry, rejection requiring a fresh search, and that an onward token is invalid for the return leg. This is genuinely additive, though it omits any rate-limit or error-response detail.

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?

Front-loaded with purpose and usage before the input rules, and each sentence carries distinct information (contents, triggers, token forms, failure modes, expiry). It is dense and slightly long, but the only mild redundancy is restating that the search summary lacks these details.

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, and it instead covers what the schema cannot: when to call, which token forms are valid, round-trip handling, and expiry behavior. Nothing an agent needs to invoke this correctly is missing.

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 100% so the baseline is 3, but the description adds real meaning beyond the schema: the short `offerRef` is ~30 characters, a short value is a legitimate input rather than an internal id, the two tokens resolve identically, and matching is exact so retyped or merged values fail. This clarifies the accepted value forms in ways the schema description only gestures at.

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+resource ('Fare options and travel policies for one flight') and enumerates the concrete contents (multi-fare upsell, baggage, cancellation, reschedule tabs). It also explicitly separates itself from search_flights by noting the summary 'carries none of these', so an agent can route without opening either 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?

Gives explicit trigger conditions: right after search_flights, or when the traveller taps Fare options in the widget, and states the identifiers already returned are enough without a new search. It effectively names search_flights as the prerequisite alternative rather than leaving it to inference.

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