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

Annotations already provide readOnlyHint and idempotentHint, which cover the safety and idempotence profile. The description adds a valuable behavioral caveat: 'Any of them may be missing where the forecast service has no data.' This informs the agent that results may be incomplete, which is beyond what annotations state. No contradiction exists.

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 two concise sentences, front-loaded with the main output and a crucial caveat. Every sentence earns its place, with no unnecessary filler or repetition.

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 read tool with one parameter and no output schema, the description lists the returned fields and notes missing-data behavior, which is sufficient for an agent to understand the tool's scope. It does not explicitly reference siblings, but that is not necessary for completeness. The main gap is the absence of guidance on error handling, which is minor for a read-only 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?

The input schema provides 100% coverage for the single parameter, station_id, including guidance on how to obtain it ('From search_stations, e.g. "noaa:9447130"'). The description itself does not add parameter meaning beyond the schema, so the baseline of 3 is appropriate.

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 states the specific data returned (wind speed/direction, sea surface temperature, sky) at a tide station, which is a clear resource and scope. It implies the verb 'get' through 'Current'. It does not explicitly differentiate from siblings, but the content makes it distinct from get_tides and search_stations, so it is slightly above average.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention get_tides or search_stations, nor any conditions for selection. An agent would have to infer its purpose from the name and content, which is a significant gap.

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