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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description usefully adds the credit cost (2 credits) and lists the returned data fields, but it fails to address the notable ambiguity that both parameters are optional — it never says what happens if neither or both are supplied.

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 action and followed by the access modes and returned fields. The only waste is the redundant 'Stars Lookup: Stars Lookup' prefix, which repeats the name and title without adding information.

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 an output schema present, return values need not be explained, and the description still summarizes them. The cost disclosure is a welcome extra. The remaining gap is behavioral: with zero required parameters, an agent has no guidance on minimal valid 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 both parameters are fully documented in the schema, which sets the baseline at 3. The description adds only a restatement that lookup can be by name or classification, without extra syntax or precedence rules for combining the two.

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 names a specific verb ('retrieves') and resource ('physical and positional stellar data') and states the two access modes: by star name or by astronomical classification. It is clearly distinguishable from related siblings such as PlanetPositions or MoonPhases, though it does not explicitly reference any of them.

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?

'Query individual stars or filter by spectral class' implies the two usage modes, which is better than nothing. However, there is no explicit when-to-use guidance, no exclusions, and no routing to alternative tools for related astronomical queries.

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