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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuine context beyond them: the approximation model (NOAA/Meeus), topocentric lunar parallax, angular separation, lunar phase, and the three verdict outcomes (compatible, contredit, intestable).

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?

Three compact sentences, front-loaded with the core action, then method, then the object enum and return values. No filler, though the enum explanation is partly redundant with 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?

No output schema exists, and the description does list the three verdict strings, plus the computational approach, which helps. However, for a 7-parameter tool with 0% schema coverage it omits the date_utc format and tolerance behavior, leaving key invocation details to inference.

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 0% across 7 parameters. The description only clarifies the object enum values (already an enum in the schema) and never explains the required date_utc format (fixed 20-char string), the role of tolerance_deg, or the units/meaning of claimed_azimuth_deg and claimed_elevation_deg.

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+resource: checking a claimed Sun/Moon position for a UTC date and location, with the method (NOAA/Meeus) and verdict outputs. This distinguishes it from shadow-oriented siblings like verify_shadows or check_shadow_track, though it never names them explicitly.

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?

Usage is implied by 'check a claimed ... position' – i.e., validate a human-provided azimuth/elevation against computed ephemeris. There is no explicit when-to-use/when-not guidance or reference to the sibling tools that might overlap (verify_shadows, check_shadow_track).

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