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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false, so the safety profile is covered structurally. The description adds a genuinely new behavioral detail in the per-call cost of 10 credits, which matters for an agent deciding whether to call it; the enumerated return fields duplicate the output schema and do not add much beyond it.

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 cost lead the text, which is good structure, but the opening repeats the tool name verbatim ("Marine Weather: Marine Weather fetches...") and the field list re-enumerates values already declared in the output schema, so several phrases do not earn their place.

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-parameter, read-only lookup with a full output schema and complete parameter documentation, the description covers what the tool does, where it applies, and its cost. The remaining gap is edge-case behavior for land coordinates and error conditions, which is minor at this complexity level.

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% and both parameters carry their own descriptions plus example values, so the schema does the heavy lifting. The description only restates that the inputs are latitude and longitude without adding accepted ranges, hemisphere/sign conventions, or precision expectations.

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 uses a specific verb and resource ("fetches offshore weather conditions for any marine coordinates") and names the two coordinate inputs, so an agent can tell it is a coordinate-driven marine weather lookup. It does not explicitly name the sibling Weather/WeatherAlerts tools it overlaps with, so differentiation is implied by the word "offshore" rather than stated.

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: the phrase "offshore weather conditions for any marine coordinates" tells the agent this is for sea locations, which is a soft constraint. There is no explicit when-to-use versus Weather, WeatherAlerts, or SunriseSunset, and no guidance on what happens if the coordinates fall on land.

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