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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds useful behavioral context by explaining what each entry contains: the period number, the opening day sign in both naming traditions, and a composed reading. This goes beyond the schema and gives the agent a clear picture of the response shape despite there being no output 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?

Three sentences, each earning its place: the first states the core purpose, the second describes the return content, and the third names the intended audience. It is front-loaded and free of filler.

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 read-only list tool with four optional, fully documented parameters and no output schema, the description provides the essential missing context: it states the full scope (twenty trecenas), the shape of each entry, and the intended use case. An agent can invoke it correctly without additional clarification.

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 100%, so the parameters (lang, limit, offset, compact) are already fully documented. The description does not add parameter-level meaning, which is acceptable because the schema carries the load. Baseline 3 applies.

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 opens with a specific verb and resource: 'Retrieve all twenty trecenas, the thirteen day periods the 260 day Tzolkin divides into.' It clearly signals this is a list-all operation and differentiates from the singular sibling mayan_trecenas_number by emphasizing 'all twenty.'

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 description gives a clear intended use case: 'Built for calendar apps, energy period trackers and content planners that work in thirteen day blocks rather than in weeks.' It does not explicitly name alternatives or say when not to use this tool, but the context is strong enough to guide selection.

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