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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds operational context the annotations lack — the credit cost and the HTTP endpoint — but says nothing about the cost of repeated calls or response behavior.

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 sentence is tight and front-loaded, giving the meaning and cycle length in one line. The bracketed metadata block is terse and scannable rather than prose bloat, though it foregrounds plumbing (endpoint) over task guidance.

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?

An output schema exists, so the description needn't explain return values. Coverage of purpose, the required parameter, cost, and endpoint is sufficient for a single-date calculator. The missing element is sibling routing, which is scored under usage guidelines.

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 67%: `fields` and `precision` carry their own descriptions (including the 'compact mode' semantics and the 14-vs-2 decimal note), and `date` is constrained by a regex pattern. The description adds nothing beyond restating that `date` is required, so baseline 3 is appropriate.

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 computation — combining the Tzolkin and Haab cycles into a unique 52-year Calendar Round label — with the concrete scope (18,980 days). It implicitly distinguishes itself from the sibling astroway_mayan_tzolkin and astroway_mayan_haab by naming them as the combined components, but it never explicitly frames the alternative choice.

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 only routing signals are the '[Required: date]' and '[Cost: 10 credits]' tags. There is no statement of when to pick Calendar Round over astroway_mayan_full, astroway_mayan_long_count, or the single-cycle Tzolkin/Haab tools. The agent must infer the use case entirely.

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