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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), and the description adds substantial behavior beyond them: positioning is included when the owner bills it, block hours derive from owner block speed, and it returns 'a reason instead of a figure' when no charter terms or rate exist. This degraded-path disclosure is exactly the kind of context annotations cannot carry.

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?

Purpose is front-loaded, but the middle sentences are long and run-on, and 'Answer with its sentence' is cryptic without more context. The content earns its place but the phrasing could be tighter.

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 does the work of explaining what comes back: a cost sentence, or a reason instead of a figure. Combined with the fallback behavior and parameter conditions, an agent has enough to call it correctly, though the exact response shape remains vague.

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 the baseline is 3, but the description adds real meaning: block_hours is only for use when the owner set no block speed and is ignored when from/to are given. It clarifies the conditional relationship between parameters rather than just restating them.

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: computing an approximate charter cost for one aircraft at the owner's published hourly rate. The 'approximate... not a quote' framing clearly separates it from a booking tool like request_trip, though it never names a sibling explicitly.

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 ('Call it whenever the person you are helping asks what a trip would cost, with the departure and arrival airports') and a clear retry rule when no block speed is published, using block_hours. It does not explicitly route the user to request_trip for an actual quote, so it stops short of naming alternatives.

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