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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. The description adds genuine context the annotations cannot: the calendar's composition (18×20 + 5) and the cost tier of 10 credits, which is a real behavioral trait. It does not, however, disclose response shape, precision defaults, or whether the result is deterministic across the same date.

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 tight lines front-load the calendar definition and the Wayeb highlight, followed by compact group/cost tags – no filler sentences. It is efficient, though the terseness comes partly from omitting the actionable verb and routing information.

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 values need not be explained, and annotations cover the safety profile. However, for a tool sitting among seven Mayan siblings with no sibling routing and an undescribed required date parameter, the definition leaves meaningful gaps an agent would want closed before invoking it.

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 67%, and the required 'date' parameter carries a regex pattern but no textual description; the description says nothing about accepted date format, timezone handling, or valid ranges. The two documented parameters are generic 'compact mode' options unrelated to this calendar, so the description adds no parameter-level meaning for the tool's actual input.

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 names the resource (the 365-day Haab civil calendar) and states one concrete function – detecting whether the date falls in the 5-day Wayeb period – but never phrases the core action (computing the date's Haab position) as a verb. With seven Mayan siblings (mayan_full, mayan_tzolkin, mayan_calendar_round, etc.), it offers no differentiation, so an agent cannot tell which Mayan tool to pick from this text alone.

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?

There is no when-to-use guidance, no exclusions, and no mention of alternatives such as mayan_full (which plausibly subsumes the Haab) or mayan_tzolkin. The 'Wayeb' sentence implies one reason to call it but stops short of routing advice.

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