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

Annotations already declare it read-only, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely useful non-obvious context: fares are the total the guest pays, no booking/card fees are added at checkout, and harbor/island levies are not Sailtix fees. It does not discuss pagination or rate limits, but this is solid added value on top of the annotations.

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 definition is dense and front-loaded: capability and return fields come first, then fare policy, then argument formats. The fare/levy passage is somewhat long, but it conveys policy an agent would otherwise get wrong, so it largely earns its place.

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 covering return values and annotations covering the safety profile, the description only needs to add constraints and semantics, which it largely does. Remaining gaps are the passenger-count parameters and the behavior of 'limit', which are left entirely to 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 only 56%, and the description compensates by explaining that origin/destination accept a harbor name, region name, slug, or an identifier from locations_list, plus the 'at least one side' requirement that is otherwise invisible with 0 required parameters. It adds nothing for adult/child/infant/limit, which remain undocumented beyond type and bounds.

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?

It names a specific verb and resource ('Searches scheduled ferry and fast-boat departures between two places on a given date') and enumerates the returned fields, which cleanly separates it from the charter_search and fishing_search siblings. An agent can identify the tool without opening the 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?

It gives a concrete precondition ('at least one side must be given') and describes the accepted identifier forms for origin/destination, which guides invocation. It never explicitly says when to prefer this over charter_search or fishing_search, so it falls short of a full when/when-not statement.

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