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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and open-world scope are covered. The description adds genuinely useful behavioral context beyond that: the geographic coverage footprint (Canada, US, Norway, Ireland, Netherlands, New Zealand, Queensland) and the modelled-versus-real distinction, which affects trust in results.

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, both load-bearing: the first describes what is returned and what attributes accompany it, the second bounds where the data is valid. Front-loaded and free of filler.

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 does the right thing by naming the returned fields (distance, time zone, tide/current timings), and the coverage caveat is valuable. But it leaves the 'kind' filter and 'limit' behaviour unexplained, and 'distance' is unqualified as to units, so it is not fully sufficient for a 4-param discovery tool.

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 50% — lat/lng are documented in the schema, but kind (enum) and limit carry no description anywhere. The description indirectly signals the tide/current distinction that the 'kind' enum encodes, but says nothing about the result cap (limit) or return-distance units, so it only partially compensates for the coverage gap.

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?

Specific verb+resource: it locates the nearest tide/current stations to a geographic point and enumerates what those stations expose (high/low times, slack water, max flood/ebb). That is clearly distinct from siblings like tide_times or currents, which retrieve readings rather than station locations, though the sibling distinction is left implicit.

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 implied by the shape of the tool (point-based proximity lookup), and the coverage list plus 'modelled tides elsewhere' tells the agent where results are authoritative versus approximate. However, there is no explicit statement of when to call this versus tide_times/currents, nor any exclusions or prerequisites.

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