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

Annotations already declare the full safety profile (read-only, idempotent, non-destructive, closed-world), so the description adds the cost tier (100 credits, Tier 4) and group, which is useful operational context. It does not disclose the computation basis for the outer planet pairs or any rate/side-effect nuance. Adequate but not rich.

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?

A single front-loaded sentence stating the computation, its formula, and its purpose, followed by compact group/cost tags. No wasted prose, though the bracketed metadata adds little beyond what tooling may already expose.

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?

The tool is a computation/analysis endpoint with an output schema and full annotations, both of which relieve the description of return-value and safety burden. However, the undocumented 'pairs' parameter and the missing contrast with sibling cycle tools leave meaningful gaps for correct invocation.

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 only 40% and the description compensates minimally, implying only the startYear/endYear date range. The 'pairs' parameter has no description anywhere, and 'fields'/'precision' compact-mode behavior is left entirely to the schema. For 5 parameters, the description does not fill the documentation gap.

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 gives a specific verb+resource: it computes the André Barbault Cyclic Index, defines it ("sum of all outer planet separations"), and scopes it to a date range. This is distinguishable from most siblings, though it does not explicitly contrast with close cousins like astroway_calendar_planetary_cycles or planetary_phases.

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 phrase "to indicate global crisis periods" implies the analytical purpose and gives some context for use, but there is no explicit when-to-use/when-not guidance and no named alternative among the many calendar tools. Usage must be inferred.

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