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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety and external-data profile is covered. Beyond that the description only says which quantities exist; it discloses nothing about how the 'past moment' is addressed, whether historical queries have retention limits, or what form the observation stream takes (no output schema exists to pick up that slack).

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 short sentence that front-loads the resource and then lists the measurements. It is appropriately sized and wastes no words, though the second clause is the source of the sibling ambiguity noted above.

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 tool with an opaque untyped 'input' object, no output schema, and eight sibling sensor variants, the description is far too thin. An agent can guess the domain but cannot construct a valid call or know how to ask for a historical reading versus the current one.

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?

There is one required parameter named 'input' with no type, no properties and 0% schema description coverage, so the schema contributes nothing. The description does not compensate in the slightest — it never explains what 'input' should contain (coordinates? station id? a timestamp for the 'past moment'?) even though that timestamp question is the whole point of the '_at' variant.

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 names a concrete resource ('traffic counting stations on Finnish roads') and the measurements returned ('flow and speed'), so the domain is clear. But it never distinguishes this tool from its obvious sibling cell_sensor_roads_fi, and the phrase 'now, or at a past moment' actually blurs the boundary rather than sharpening it, leaving the '_at' suffix unexplained.

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 statement of when to pick this over cell_sensor_roads_fi or the other cell_sensor_*_at variants. The 'now, or at a past moment' wording implies the tool covers both cases, which gives the agent no selection rule at all and may push it toward the wrong sibling.

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