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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds the specific nature of the output (source keys for search_sightings) but does not disclose return format, ordering, or potential pagination. For a zero-parameter read-only tool, this is adequate but not rich.

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, tightly worded sentence that is front-loaded with the action and resource. There is no filler or redundancy; every word contributes to meaning.

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's simplicity (no parameters, no output schema, trivial read-only operation), the description is sufficient for an agent to understand what it does and why. It could theoretically mention the output type (e.g., 'returns a list of strings'), but that is inferable from the name and purpose. The missing detail is minor.

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?

The tool has zero parameters, so schema coverage is trivially 100%. Per the calibration baseline, a 4 is appropriate when no parameters exist and the description need not compensate for undocumented inputs. The description adds nothing about parameters, but none are needed.

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 states a specific verb ('List') and a specific resource ('archive source keys') with an explicit purpose tied to another tool ('available to search_sightings'). This clearly differentiates it from sibling tools like search_sightings or list_beings, so an agent knows what it returns and why it exists.

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 implies usage: you list sources to obtain valid keys for search_sightings. However, it does not explicitly state when to use it over alternatives, nor does it provide exclusions or context like 'call before search_sightings'. The link to search_sightings is helpful but insufficient as explicit guidance.

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