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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, so the safety profile is covered. The description adds useful behavioral context: it returns specific fields (radius, mass, orbital period, equilibrium temperature, insolation flux, host star details), sorts by radius ascending, and allows customising temperature and radius bounds. This goes beyond the annotations and helps the agent understand output composition and filtering flexibility.

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: the first states the core purpose and filtering criteria, the second covers output fields and customisability. It is front-loaded with the most important information and has no redundant or verbose wording. Every clause earns its place.

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?

The tool has an output schema, so the return structure is handled externally. The description covers the query logic, defaults, customisation, data source (NASA Exoplanet Archive — pscomppars table), and return fields. There is no missing information an agent would need to call this tool correctly.

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%, with each parameter (limit, temp_max, temp_min, radius_max, radius_min) already documented with defaults and meanings. The description only restates that temperature and radius bounds are customisable, which adds little beyond the schema. It does not introduce new parameter semantics or clarify edge cases.

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 opens with a specific verb (Find) and a clear resource (potentially habitable exoplanets in the conservative habitable zone), explicitly defining the selection criteria (Earth-like radius 0.5–2.0 R⊕, equilibrium temperature 180–310 K) and the sort order (radius ascending). This is a distinctive purpose that separates it from generic search tools like nasaexoplanet.planets.search and detail tools like nasaexoplanet.planets.detail.

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 implies that this tool is for finding habitable-zone candidates, and it mentions the customisable bounds for 'optimistic or strict filtering', which guides parameter adjustment. However, it does not explicitly name sibling tools or state when not to use it, though the specificity makes the usage context fairly obvious.

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