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

Annotations already declare read-only, idempotent, non-destructive behavior, yet the description still adds real value beyond them: per-call credit cost and block billing rules, the fact that only successful calls are charged, sandbox-key behavior, and an explicit determinism guarantee. These are operational traits an agent cannot derive from the structured fields.

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?

Front-loaded with the one-line purpose, then compact labeled lines for cost, determinism and examples. Slightly more than strictly necessary, but every line carries information an agent would otherwise have to guess.

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 an output schema present, the description need not explain return values, and it covers everything else an agent needs: the exact sunrise definition, billing implications, determinism, and a ready-to-use example. Nothing required to invoke it correctly is missing.

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%, so date, timezone, latitude and longitude are already documented with format, ranges and sign conventions. The description's example arguments add a concrete working call but no semantics beyond the schema, so the baseline 3 applies.

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 states a specific resource (sunrise, sunset, and the next sunrise) for a defined local date and place, and pins down the exact astronomical convention (upper limb at sea-level horizon, 36.6′ refraction). This clearly separates it from siblings like get_ephemeris_positions or get_ephemeris_angles, which cover broader ephemeris quantities.

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 note that "the Vedic day runs from sunrise to the next sunrise" implies a use context, but the description never states when to prefer this tool over siblings such as get_ephemeris_angles or get_ephemeris_series, nor any exclusions. Usage is inferable rather than stated.

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