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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: 'Computed locally, no network call' (latency/offline behavior) and the fact that contact times are returned in local time and include Sun height, which affects how the agent should interpret results. It does not cover failure behavior for unknown cities or out-of-path coordinates.

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 dense sentences, front-loaded with the verb and resource, then scope, then input forms and the offline-compute note. No sentence is redundant and nothing important is buried.

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 rich annotations, full schema coverage and an output schema, so the description only needs to cover scope and input framing, which it does completely. Geographic coverage, eclipse-specific scope, input alternatives and local computation are all stated; return values are handled by the output schema.

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 coverage is 100%, so the baseline is 3. The description still adds meaning by framing the input choice ('Give a city (830 known) or coordinates') and disclosing the finite 830-city gazetteer, a real constraint not visible in the schema. The remaining alias and enum details are already fully covered by the schema.

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 and resource ('Compute the total solar eclipse of 2 August 2027 at a place') and enumerates the outputs (totality/partial, magnitude, contact times, duration, Sun height), so the agent knows exactly what it gets. It scopes itself to one eclipse ('Use it for that eclipse only') but never names a sibling such as solar or sky_events, so the differentiation is implicit rather than explicit.

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?

'Use it for that eclipse only' plus the geographic description (total from Spain/Morocco to Egypt, Saudi Arabia, Yemen; partial over Europe) tells the agent when this tool is relevant versus a general sun/sky tool. 'Give a city (830 known) or coordinates' gives clear input-selection guidance. It does not explicitly state when NOT to use it or name a fallback tool for other eclipses.

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