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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantive behavior: rounding down, no minimum, no elite bonus, refusal-with-message for non-Argentina flights or unlisted letters, tier thresholds, and provenance ('cwsi.net's calculator', 'Unofficial'). That is well beyond what the annotations convey.

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-loads the core formula before branching into zones, refusal rules, tiers and input format. It is dense and somewhat run-on (mixing earning rule, status progression and provenance in one paragraph), but every sentence carries information relevant to correct invocation.

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, 100% schema coverage and full annotations, the description only needs to carry the domain model, which it does (earning rule, zones, rounding, tier progression, refusal behavior). It omits mention of the Flying Blue creditTo/creditClass/creditStatus path, though the schema documents those fully.

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 coverage is 100%, so 3 is the floor, but the description supplies the zone definitions (Domestic = both airports in Argentina; the specific Regional and International country lists) that are not in the schema and are required to pick the correct fare percentage. It also clarifies segs ordering and that no price is taken, adding real meaning on top of the schema.

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+resource ('Aerolineas Argentinas Aerolineas Plus miles for Aerolineas Argentinas flights') and immediately gives the earning rule (distance x a fare-letter/zone percentage). The airline is named explicitly, so it is trivially distinguishable from the dozens of sibling airline calculators.

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 clear context on when the tool applies (flights touching Argentina, listed fare letters, no price) and routes the agent to the companion tool by saying the segs miles come from 'calculate_flight_distance'. It also notes the refusal condition for out-of-scope flights, but does not explicitly contrast itself against other calculator siblings.

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