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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is low, and the description still adds non-trivial operational context: a 10-credit Tier 1 cost and the correlation epoch needed to interpret the returned number. It does not mention validation behavior for malformed dates, which keeps it short of a 5.

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 written sentences that lead with the output notation and epoch, followed by compact group/cost tags. No filler, though the opening is a noun phrase rather than an action statement, which slightly weakens front-loading of the tool's function.

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 no explanation, and the operation is simple (date in, Long Count out). What is missing is sibling routing and any note on invalid-date handling, which matters given the crowded Mayan tool family.

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 a middling 67%: 'fields' and 'precision' are well described in the schema, while the required 'date' parameter carries only a pattern and no prose. The description adds nothing about any parameter, so the schema does the work; a baseline 3 is appropriate for this coverage level.

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 identifies the specific resource (Mayan Long Count) and even its output shape ('baktun.katun.tun.uinal.kin') and epoch ('Days since 4 Ahau 8 Cumku (3114 BC)'), so an agent knows what this produces. It never names a verb or distinguishes it from the many sibling Mayan tools (tzolkin, haab, calendar_round, full), which is exactly the gap that separates a 4 from a 5.

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 at all. With seven sibling Mayan-calendar tools in the list, the agent is given no signal about when to pick Long Count over tzolkin, haab, calendar_round, or mayan_full, nor any prerequisites. Only implied usage exists, so this sits at the 'no guidance' level.

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