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

Annotations already carry the read-only, idempotent, open-world, non-destructive profile, so the bar is lower; the description still adds real value by disclosing that results are live and public, one per requested layer, and include a signed receipt plus source. It omits edge behavior such as what happens when nothing lies within max_km or whether any auth/quota applies.

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 dense sentence that front-loads the core purpose and packs the return payload into the same clause. No wasted sentences, though the trailing 'and a signed receipt' reads as slightly bolted on.

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?

With no output schema, the description usefully describes the response shape (reading, distance, source, receipt), and annotations cover the safety profile. It is close to complete, but gaps remain on no-match behavior and any auth/rate constraints.

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 every parameter including layers and max_km is already documented in the schema. The description restates the layer concept ('one per layer asked for') without adding format or default detail beyond what the schema gives.

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?

States a specific verb+resource (nearest live public sensors to a point) plus the scoping rule 'one per layer asked for' and the returned fields (reading, distance, source, signed receipt). It implicitly differentiates from the single-layer siblings air_quality_now/weather_now by being multi-layer, but never names them, so it stops short of a 5.

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?

The multi-layer framing implies you reach for this when you want several sensor types at once, but there is no explicit when-to-use, no when-not, and no reference to the sibling tools it overlaps with. Usage is inferable rather than stated.

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