ephemeris_moon_phase

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

Annotations already mark the tool as read-only. The description adds context: credit cost, behavior when datetime is omitted (returns current time), and the optional latitude/longitude parameters for local void-of-course. No contradictions.

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 well-organized with bullet points, emojis, and examples. It is slightly longer than necessary but every sentence adds value, and it front-loads the core purpose.

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?

Given no output schema, the description lists the return fields (phase name, angle, illumination, void-of-course) and credit cost. This is sufficient for an agent to understand what to expect.

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 schema already describes all three parameters. The description adds example usage and clarifies the purpose of latitude/longitude (local void-of-course), but this does not significantly raise the score above the baseline of 3.

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 explicitly states the tool retrieves the moon's phase angle, illumination, and void-of-course status at a specific time. It clearly differentiates from the sibling tool ephemeris_next_lunar_phase by noting that tool is for upcoming phase dates.

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 description provides explicit guidance on when to use this tool (current phase at a point in time) and when not to (for upcoming new/full moon dates). It names the alternative tool and includes examples.

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