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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds behavioral context by specifying that the position is 'live' and enumerating the navigation data provided (current lat/lon, speed, course, heading, destination, status), which goes beyond the schema without contradicting any annotation.

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 description is compact and front-loaded with the essential question ('Where is ship...'), followed by the return payload and a clear example. Every sentence earns its place, with zero fluff.

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 simple single-vessel lookup tool with no output schema, the description fully covers what it does, what identifiers are accepted, what data is returned, and how to invoke it via the example. It is complete for an agent to select and use 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 parameters are already well-documented. The description reinforces the alternative identifiers (IMO, MMSI, UUID) and provides an example usage, but it does not add substantive new meaning beyond indicating that at least one identifier is required—which the schema already states.

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 clearly states the tool's function with a specific verb ('Locate') and resource ('a single vessel'), and distinguishes it from the sibling `datalastic_vessels_in_radius` by emphasizing 'single vessel' and listing the specific AIS fields returned. It also provides a concrete example, making the purpose unmistakable.

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 description implies usage for querying a single vessel by IMO/MMSI/UUID and clearly specifies the data returned (live AIS position, destination, speed, etc.). However, it does not explicitly mention alternatives like `datalastic_vessels_in_radius` or state 'use this when you need one ship, not a set', so it stops short of full exclusion guidance.

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