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

Annotations already cover safety (readOnly, non-destructive, idempotent) and the description correctly doesn't contradict them. It adds the useful domain rule for what a VOC period is, but with 7 parameters (rangeDays, timezone, precision, fields, timezoneOffset) the description says nothing about range limits, timezone handling, or compact mode — leaving that entirely to schema.

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 tightly written sentences with the definition front-loaded and no wasted words. Metadata block (group/endpoint/required/cost) is boilerplate but useful for routing. Could be marginally improved only by naming a sibling.

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?

For a 7-parameter, 10-credit query returning a range of periods, the description omits how far it can span, that rangeDays controls the window, and how timezone affects output. An output schema exists, so return format needn't be described, but the usage constraints (range limits, credit cost already noted) are only partially covered.

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 57%, so the schema documents timezone, timezoneOffset, precision, and fields but leaves rangeDays (and both required date/time) undescribed. The description adds no parameter meaning at all, and doesn't compensate for the rangeDays gap. Baseline 3 is appropriate for this coverage level.

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 (Find) and resource (Moon void-of-course periods) plus the defining rule 'from last aspect until entry into the next sign.' Clear and distinguishable from siblings like astroway_calendar_moon_aspects, but doesn't explicitly name which sibling differs.

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?

No when-to-use guidance, no alternatives named, no exclusions. The agent must infer the tool's place among the many calendar_* siblings entirely on its own.

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