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

Annotations already declare the safe read-only, idempotent, non-destructive profile, so the description is not obligated to cover safety. It does add real behavioral context the annotations do not carry: the credit cost (10 credits, Tier 1), the endpoint, and the phase-dependency of the output. It stops short of describing pagination or response shape, but the output schema covers return values.

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 core purpose and the pairing hint are front-loaded in two tight sentences, and the bracketed metadata lines (group, endpoint, required, cost) are structured and scannable rather than prose padding. Minor overlap with the title 'Moon-Phase Sleep Tips' is the only redundancy.

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 annotations covering safety and an output schema covering the return payload, the description supplies the remaining essentials - required input, cost, and endpoint. The only soft spot is that the date-to-phase relationship is left implicit, making the sun-times pairing hint slightly ambiguous.

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 67%: `fields` and `precision` carry solid descriptions in the schema, while `date` is only constrained by a regex pattern. The description adds only 'Required: date', which merely restates the structured required array, so it contributes almost nothing beyond 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?

The description states a specific verb and resource: it returns sleep recommendations keyed to a moon phase, which cleanly separates it from wellness_diet, wellness_exercise, or wellness_cycle. It does not, however, name or contrast any sibling tool, so the agent must infer differentiation from the resource phrase alone.

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?

It gives one concrete usage instruction - pair with /sun-times to determine the current phase - which is genuinely helpful orchestration guidance. But it never states when to prefer this over the other wellness tools, nor any exclusions or prerequisites beyond the required date.

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