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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds genuinely non-obvious semantics: busyness is indexed to the place's own peak month and never compared across places, overnight share and day-stop length come from tracked AIS traffic, and a nearest bookable base is substituted when a spot has no fleet. Those are interpretation rules an agent could not infer from the schema and that materially affect how results must be reported.

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 and scope are front-loaded in the first clause, and the two closing sentences (use cases, busyness caveat) earn their place. The long middle enumeration is dense but each item names a distinct returned field, though it reads as one run-on sentence and could be segmented for faster scanning.

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?

There is no output schema, so the description must carry the return contract, and it does: it lists every category of returned data and explains how the derived metrics are computed and compared. Combined with full schema coverage on the two inputs, an agent has everything needed to call it and to interpret the response 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% and the currency parameter already documents its enum, the EUR default, and the conversation-currency override, so the schema carries the parameter burden. The description alludes to money via "cheapest day rate" but adds no syntax or usage detail beyond the schema. Baseline 3 applies.

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 and resource ("Get full details of a marina, anchorage or bay by ID") and enumerates the payload: description, amenities, contact, boat count, cheapest day rate, plus AIS-derived busyness, usage mix, hidden-gem flag, destinations, and nearest bookable base. That enumeration distinguishes it from search_locations (discovery) and get_poi_details (points of interest) without the agent needing to open another 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?

Gives three concrete trigger conditions: the user is viewing or asks about a specific place, asks when it is quiet, or asks where to go next from one. It also anchors the required id to search_locations results in the schema. It stops short of naming a sibling it should be avoided in favour of (e.g. search_locations for discovery, get_poi_details for land-side POIs), so no explicit exclusions.

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