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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond that — it actively listens at a location rather than querying stored data, and it exists to distinguish receiver-coverage gaps from true absence of traffic. It omits the API-key requirement and the roughly 3-25 second listening latency, which the schema partly covers.

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?

Two sentences, front-loaded with the core question and then the when-to-use rule. Every clause earns its place and nothing is repeated from the schema.

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 read-only diagnostic with no output schema, the description conveys what the tool determines and why it matters. It could be slightly more explicit about what the reported result actually contains (binary coverage vs. receiver details), but it is largely sufficient for correct invocation.

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 all five parameters including the defaulted radius_km and window_seconds are documented in the schema. The description adds no parameter-specific syntax or meaning beyond the point-location concept, so the baseline 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?

States a specific verb and resource: it listens at a point and reports whether a community receiver covers the location. The framing ('does live AIS tracking actually work here') plus the no-ships/no-receivers distinction makes it clearly separable from siblings like live_ships_in_area and live_ship_position.

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?

Explicit triggering conditions: 'whenever a vessel search comes back empty' and 'always before treating an empty result as evidence that shipping has stopped.' It names the exact situation that selects this diagnostic over the vessel-listing siblings, leaving nothing to inference.

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