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

Annotations already declare readOnly/openWorld/non-destructive, so the bar is low, yet the description adds real behavioral context: it will synthesize a connection when no direct boat exists, and it reports hotel pickup policy and per-person price. The 48h booking notice is carried by the schema, not the description.

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?

Two sentences, front-loaded with the route domain, with no filler or restatement of the tool name. The long place enumeration is dense but earns its place by defining coverage.

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 usefully enumerates the returned fields (times, operator, piers, pickup policy, price) and the fallback behavior for indirect routes. Combined with full schema coverage and read-only annotations, an agent has nearly everything needed to call it correctly.

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 description coverage is 100%, so the schema already documents from/to/date/type/passengers; the description only echoes the destination list that the 'from' param already provides. It adds no syntax, format or enum guidance beyond the schema, so the baseline of 3 is correct.

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 names the resource precisely (boat transfers/ferry-speedboat timetables), the covered routes, and the attributes returned (departure times, operator, piers, pickup policy, price). It is clearly distinct from search_flights, search_hotels and search_experiences, though it never uses an explicit search/find verb.

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 only implied: an agent can infer this is the lookup step before book_transfer or check_availability, but the description never states when to prefer it over those siblings or when it is not applicable. The mention that it 'suggests a connection when there is no direct boat' hints at scope but is not routing guidance.

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