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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint, so the safety profile is covered. The description adds only geographic scope and a confusing 'past moment' capability that the zero-parameter schema does not appear to support, which risks misleading the caller about freshness and time selection.

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?

It is a single short sentence with the resource front-loaded, which is good, but the trailing clause is ambiguous and effectively wastes its space by raising an unresolved question about the time dimension.

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 zero-parameter, read-only, open-world sensor feed with no output schema, 'every ship reporting AIS around Finland' roughly conveys what comes back. Missing are freshness/update cadence and any hint at payload shape or volume, and the 'past moment' claim is left unexplained.

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?

With zero parameters there is nothing for the schema to document, so the baseline would be 4. However, the description implies a time argument ('or at a past moment') that has no corresponding parameter, creating a semantics mismatch rather than adding clarity.

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?

It identifies the resource (AIS ship reports around Finland) with reasonable specificity, but the trailing clause 'or at a past moment' blurs the purpose rather than sharpening it, especially since a sibling named cell_sensor_ais_fi_at presumably owns the historical case. An agent cannot tell from the description alone whether this tool covers both time modes or only live data.

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 when-to-use guidance and no explicit routing to alternatives such as cell_sensor_ais_fi_at, cell_sensor_ships, or cell_sensor_roads_fi. The agent must infer selection criteria from tool names alone.

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