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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety is covered. The description adds genuinely new behavioral context: these are affiliate handoffs and the cards do not represent live availability, prices, or confirmed bookings — an important expectation-setting detail beyond the structured fields. It does not describe the shape of the returned cards, but no output schema exists to fill that gap either.

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 tightly written sentences with no filler; the core purpose is front-loaded and the caveat follows immediately. Every clause earns its place.

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?

For a 7-parameter, link-generation tool with full schema coverage, rich annotations, and no output schema, the description covers purpose and the key limitation that prevents misinterpreting results as live prices. It could optionally note what the response contains (e.g., link list), but nothing essential to correct invocation 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 description coverage is 100% with detailed per-parameter docs (currency fallback chain, trip_id defaults, passenger limits), so the schema does the heavy lifting. The description only echoes the required route and date conceptually ('dated pickup and drop-off route') and adds no format or semantic detail beyond it — baseline 3 is appropriate.

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?

Specific verb ('Return') plus specific resource ('Welcome Pickups and GetTransfer affiliate cards') scoped to a 'dated pickup and drop-off route'. An agent can immediately distinguish this ground-transfer link tool from flight_booking_link, train_booking_link, and segment_booking_links 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 sets a clear usage context and a strong exclusion ('provider search or quote handoffs only, not live availability, prices, or confirmed bookings'), which tells the agent when NOT to rely on it for actual availability or pricing. It stops short of naming an alternative tool for when real prices are needed, so it falls just short of a 5.

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