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

readOnlyHint=true already establishes the safety profile, so the bar is low, and the description still adds real context: the registry is caller-scoped ('the caller's boats'), IDs are 6-char case-sensitive alphanumerics, and unknown fields are null rather than absent. Pagination/ordering behavior of the list mode is not disclosed.

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?

Purpose and mode enumeration are front-loaded and efficient. However the trailing sentences about timestamps, distances and durations appear to be generic field conventions not tied to any input of this tool, and they dilute an otherwise tight definition.

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?

For a two-mode read tool with no output schema, the description covers mode selection, id format, field vocabulary and null semantics, which is most of what an agent needs. It leaves list-mode return shape (pagination, ordering) and error cases unstated.

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% with 0 declared top-level parameters (an anyOf of action:list / action:get+id), so the baseline is high. The description maps directly onto the two schema variants and clarifies the id format and action values, though it then documents `flag`/`hullType`, which are not inputs in the schema and may momentarily confuse call shape.

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+resource ('Read the caller's boats') and immediately scopes it as a 'reusable, per-owner registry', then enumerates the two modes (list all, get one by id). The read/write split against sibling ship_write is unambiguous from the name plus this phrasing.

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?

The two usage modes are spelled out ('list them all, or get one by id'), which tells the agent how to shape the call. It offers no explicit when-not guidance or named alternative (e.g. ship_write for mutations), so it lands just short of a 5.

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