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

Annotations already disclose readOnly/idempotent/non-destructive/closed-world, so safety is covered. The description adds genuinely useful non-schema context: the credit cost ('10 credits (Tier 1)'), the group tag, and the returned components, which agents need for planning.

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-wound sentences, front-loaded with the identity and return shape, followed by the differentiating clause. The bracketed group/cost metadata is compact and useful rather than padding.

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 return detail is covered elsewhere, and the description still summarizes the return ('kin + tone + seal'). Combined with annotations and the cost/group tags, this is complete enough for a read-only lookup tool; only the date format is left entirely to the schema.

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' are documented in the schema, while 'date' carries only a regex pattern. The description adds no meaning about the date format or the compact-mode params, so it neither compensates for the gap nor extends the schema. Baseline 3 for schema-led params.

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 resource (the Argüelles Dreamspell reinterpretation) and a specific verb/output ('Returns kin (1-260) + tone + seal'). The line 'Distinct from traditional Tzolkin' explicitly separates it from the astroway_mayan_tzolkin sibling, so an agent can route correctly without opening any schema.

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 'Distinct from traditional Tzolkin' clause tells the agent when to pick this modern variant versus the traditional one, which is the key selection decision among the Mayan siblings. It stops short of an explicit when/when-not rule or naming other siblings like mayan_full or mayan_calendar_round.

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