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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds valuable context beyond annotations: the 'confirmed vs predicted' data distinction, the ~2-day window, and the limitation that 'aircraft assignments aren't published further out'. No contradiction with annotations.

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 earning its place: the usage trigger, the core function and data nature, and the parameter constraint plus alternative routing. The most decision-relevant information is front-loaded.

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 simple 3-param search with 0 required params and no output schema, the description covers when to use, what it returns, the time window, and param requirements. It doesn't describe the return format, but for a flight-list search this is a minor gap given the clarity of the rest.

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%, so the baseline is 3. The description adds the relational constraint 'Pass at least one of origin or destination (both narrows to a single route)', which is not present in the individual parameter descriptions. This meaningful cross-parameter guidance justifies a 4.

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: 'Returns CONFIRMED Starlink flights in the next ~2 days'. The 'firm schedule, not prediction' phrase distinguishes it from prediction siblings, and the description names predict_route_starlink/plan_starlink_itinerary as alternatives. An agent can immediately tell this apart from the other tools.

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 an explicit trigger condition ('Use when the user asks "what Starlink flights leave from X tomorrow?"') and explicit exclusions with named alternatives ('for later dates use predict_route_starlink or plan_starlink_itinerary instead'). Nothing is left to inference.

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