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

Annotations only cover the safety profile (readOnlyHint=true, openWorldHint=false); the description goes further by disclosing the actual verdict scale (low/typical/high), the comparison baselines used (cabin's usual price, today's listed fare, 120-day low), and the returned watch_url for fare-drop email. The 120-day lookback window is genuinely useful behavioral context. It does not contradict the read-only annotation, since watch_url is a returned link rather than a mutation this tool performs.

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?

The purpose is front-loaded in the first clause, which is good, but everything after it is one long comma-chained run-on mixing inputs, outputs, and defaults. A reader has to re-parse the sentence to separate what goes in from what comes back.

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 seven parameters and no output schema, the description carries the return-value burden and does so: verdict, today's fare, 120-day low, a quotable paragraph, and watch_url. The default cabin behavior and price basis are also covered. It is close to complete, though the currency/per-person basis is only in the schema.

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 value by consolidating the three mutually exclusive ways to name a sailing (sailing_id, a fantasize.net /cruise/ link, or ship plus depart_date) into one sentence, which the per-parameter schema descriptions do not state as alternatives.

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?

The description gives a concrete verb and resource ('Judge a price someone was quoted or already paid for one sailing') and scopes it to a single sailing, which implicitly separates it from aggregate siblings like fare_index. It does not name or contrast any sibling tool explicitly, so it lands at 4 rather than 5.

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?

Usage is implied: you invoke it when a person has a quoted or paid fare in hand. There is no explicit when-not guidance, no prerequisites, and no routing to alternatives such as fare_index or get_cruise, so the agent must infer the boundary between this and its siblings.

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