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

Annotations already cover read-only, idempotent and closed-world behavior, so the remaining burden is light. The description adds two genuine constraints not in structured data: a 20-year cap per call and a 15,000-year overall validity span, both of which affect how an agent should batch requests.

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 resource and return content, followed by the range constraint. Nothing is padded, though the phrase 'Works across the full 15,000-year span' could be tightened into the length limit rather than standing alone.

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 no output schema, the description is responsible for telling the agent what comes back, and it does list the key returned fields. What is missing is mainly edge-case behavior (invalid intervals, results truncation at the cap), which is a modest gap for a two-parameter read query.

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 compensate; it only implies that the two dates bound the search range. It does not state the expected date format, whether bounds are inclusive, or what happens for a reversed or out-of-range interval, all of which the bare pattern regex leaves ambiguous.

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 resource (solar and lunar eclipses) and the returned fields (type, greatest eclipse moment, eclipse degree), so an agent knows exactly what this produces versus siblings like transits or sky_now. It does not explicitly name a sibling, but the domain is narrow enough to be unambiguous.

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 'up to 20 years per call' phrasing implies the agent should chunk long ranges, and the 15,000-year span hints at the valid domain. However, there is no explicit statement of when to prefer this over transits or timing_events, nor any guidance on prerequisites or date format expectations.

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