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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), so the bar is lower. The description adds real value by enumerating what the response contains and by stating that heads_up lines are listed first — output-composition and ordering behavior the agent could not get from annotations, and there is no output schema to supply 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?

A single sentence, front-loaded with the core promise ('One call that answers...'), and every clause enumerates a returned data type that would otherwise be undocumented. Slightly dense with nesting, but no sentence is wasted.

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 parameter-light, read-only aggregation tool with no output schema, the description successfully carries the burden of describing the return contents and ordering. It stops short of covering pagination, latency, or failure modes for a spot with no nearby station, which is the only notable gap.

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 lat, lng and from are already documented with ranges, format (WGS84, YYYY-MM-DD) and the free-key 7-day limit. The description adds nothing about parameters, so the 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?

The description names a specific composite resource — tide station, currents, wind/gusts/waves, warnings, water temperature, sunrise/sunset for a given spot — so an agent understands this is the aggregated 'one launch' bundle rather than a single-domain tool. It is clear enough to separate from siblings like tide_times or marine_forecast, though it never names those siblings explicitly.

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 via the title and the phrase 'One call', suggesting the agent should reach for this when it wants everything at once for a launch. There is no explicit statement of when to prefer the granular siblings (tide_times, currents, marine_forecast) or any exclusions, so the agent must infer the trade-off.

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