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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds two useful behavioral notes: it tells the caller to supply measurements rather than video, and that results are 'model-conditional consistency findings' — a caveat about output interpretation. It still lacks detail on calculation assumptions, failure modes, or return structure.

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 compact and front-loads the action and output types. Three short sentences each carry some weight, though 'model-conditional consistency findings' is slightly vague and could be sharpened.

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?

For a tool with 5 parameters, 4 required, 0% schema descriptions, and no output schema, the description is incomplete. It explains the samples input shape but omits date format, location semantics, and tolerance meaning, leaving key required parameters undocumented.

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%, so the description must carry parameter meaning. It partially covers the samples array by specifying 4–120 minute/azimuth pairs, but says nothing about date_utc format, latitude/longitude, or the optional tolerance_deg parameter. The required location and date inputs are implied only indirectly through 'solar motion.'

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 ('Compare') and resource ('measured minute/azimuth pairs with solar motion'), and lists the core outputs (residuals, slope, direction, time-lapse speed). It is clear what the tool does, though it does not explicitly contrast itself with nearby siblings such as verify_shadows or triangulate_tracks.

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 only guidance is 'Supply measurements, not video,' which is an input constraint rather than a when-to-use rule. There is no mention of when this tool should be chosen over alternatives like verify_shadows or check_ephemeris, nor any exclusions or prerequisites beyond the input format.

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