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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, so the agent knows the tool is safe, idempotent, and has an open-world result. The description adds value with the three possible verdicts and the explicit 'Never UFO detected' caveat, which clarifies limitations beyond annotations. No contradictions.

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 sentences and front-loads the key action. It is concise and avoids fluff, though the 'Never UFO detected' sentence could be integrated into the first or placed as a separate note. Every sentence serves a purpose.

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?

Given the tool has 7 parameters (57% schema coverage), an output schema, and no nested objects, the description covers the essential behavior (matching, verdicts) and edge case (no UFO). It does not detail the output format, but the output schema is present, so that is acceptable. It could mention what the tool does with the 'lon'/'lng' alias more explicitly, but overall it is complete for its complexity.

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 57%, and the description does not detail individual parameters. However, the description's high-level explanation of the tool's purpose (matching azimuth/elevation/time to satellites) provides enough semantic context for the required parameters (az, el, lat, time). The 'lon' and 'lng' alias is documented in the schema. The description could have added more detail on the 'lang' or optional parameters, but the core meaning is clear.

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 uses specific verbs ('Match') and resources ('timed azimuth/elevation to known bright satellites'), and distinguishes from siblings—none of the sibling tools (e.g., object_lookup, iss_passes) suggest the same satellite identification function. The three possible verdicts are enumerated, which clarifies the output scope.

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 description clearly states the tool's function (matching observations to satellites) and implies its use case (when an agent has a timed observation), but it does not explicitly exclude alternatives or state when not to use it. The verdict list and 'Never UFO detected' provide some usage boundaries, but no sibling comparisons are made.

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