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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds substantial context beyond them: the ranking metric (coverage ratio with a concrete 92% example), that direct flights are always shown first, and critically that results are probability-ranked routings, NOT bookable itineraries because connection timing isn't validated. That last caveat is exactly the kind of expectation-setting an agent needs.

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 the usage trigger, then mechanism, then the return-value caveat — a sensible priority order. It is dense but every clause (ranking metric, stop limits, non-bookable warning) earns its place; only the doubled emphasis on stops (in both prose and schema) is mildly redundant.

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 compensates by describing the return shape (probability-ranked routings, not bookable) and the ranking basis. Combined with the safety annotations and full schema coverage, an agent has everything needed to call and interpret this tool.

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%, including the date-window semantics and max_stops/default limits, so the schema carries the parameter burden. The description restates the stop defaults but adds no syntax or format detail beyond the schema, matching the baseline-3 expectation when coverage is high.

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 (plan) and resource (Starlink itinerary) and self-declares as the PRIMARY travel-planning tool with multi-stop search ranked by coverage ratio. An agent can distinguish it from the narrower predict_route_starlink and search_starlink_flights siblings 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?

Opens with an explicit trigger ("Use when the user asks 'what's the best way to fly X to Y with Starlink?' or wants ranked alternatives"), which gives clear context. It does not, however, explicitly name when to prefer siblings like predict_route_starlink or predict_flight over this one, so routing among alternatives is left partly to inference.

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