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

Annotations already declare readOnly, idempotent, non-destructive and non-openWorld, so the safety profile is covered. The description adds the valuable behavioral detail of what data the comparison surfaces, which is the main thing an agent needs to judge usefulness.

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-loaded with the verb and scope, then a dense but purposeful enumeration of compared attributes. The second sentence on id provenance is short and earns its place; the field list is long but each item is information the agent needs.

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 correctly takes on the burden of describing return content, and it does so thoroughly. The only gap is the cabin parameter's effect on pricing and the 2–3 id limit, which remain schema-only.

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 50% and both parameters already carry inline descriptions in the schema. The description only reinforces that ids come from searchCruises and says nothing about the cabin filter or the 2–3 id cardinality constraint, so it adds little beyond the schema baseline.

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 (compare) plus the exact resource (2–3 specific sailings) and enumerates the compared dimensions: dates, ports, price, price per night, verdict vs six-month average, ship age/size, family suitability, rating, CDC score. It is clearly distinct from the sibling searchCruises, which it identifies as the source of ids.

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?

"Takes sailing ids from searchCruises" establishes the prerequisite workflow step and implies this is the follow-up to a search. It gives no explicit when-not-to-use or alternative comparison tool, but the context is clear and no competing sibling exists.

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