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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds genuinely new behavioral context the annotations do not: results are in Philippine time and 'times can differ by day,' warning the agent not to treat times as static. No pagination or empty-result behaviour is described, which keeps it below a 5.

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 sentences, zero filler. The scope-defining sentence comes first and the usage hint second, so 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?

With no output schema, the description carries the burden of saying what comes back, and it does so adequately ('flights ... with the time each runs'). Required airport/direction are implicitly covered. It omits what happens on no match or whether the flight filter narrows or merely highlights, which is the main remaining gap for a four-parameter lookup 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 75% and both enums are declared, so the schema does most of the work. The description reinforces the date semantics ('the time each runs on a given date') but adds nothing on the airport choice (Caticlan vs Kalibo trade-off) or on how partial flight numbers are matched — the two places where an agent would most benefit from guidance. Baseline 3.

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 ('List scheduled flights at Caticlan or Kalibo airport') plus the payload ('the time each runs on a given date'). No sibling in the list does anything similar — the others are listing, quoting, and booking-link tools — so an agent can route here 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?

'Use it to match a traveller's flight number to its landing or take off time' gives a concrete retrieval scenario, which is clear context for when to call it. It stops short of explicit exclusions or named alternatives, but the sibling set (booking links, quotes, activity lists) makes mis-selection unlikely.

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