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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. The description adds non-obvious behavior beyond that: the fare is repriced server-side and the response includes a Paytm booking link, which an agent would not infer from annotations alone.

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?

Two compact sentences, with the core action and output front-loaded in the first. The second sentence is caller-oriented context rather than agent guidance, so it earns slightly less than a fully front-loaded description would.

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, return values need not be enumerated, and annotations carry the safety semantics. What remains thin is token sourcing and pairing constraints, but for a two-parameter read tool this is close to sufficient.

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 description coverage is 0% for two required token parameters, so the description must compensate. It partially does, mapping the tokens to an 'onward + return flight pair', but never explains token provenance, format, or that the two must belong to the same itinerary — leaving a real gap.

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 and resource ('Computes the combined round-trip fare for a chosen onward + return flight pair'), plus two secondary behaviors (repricing, returning a total and booking link). This is clearly distinct from sibling tools like fare_calendar, get_fare_family, and search_flights without needing to name them.

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 a clear triggering condition: 'Used by the flight results card when both legs are selected,' which tells the agent the tool only applies once both an onward and a return leg exist. It does not name alternatives or state when NOT to use it (e.g., one-way itineraries), so it falls short of explicit routing guidance.

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