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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds behavioral context by noting the default-to-today behavior and the optional 'from' date, plus the 'next Christmas' logic implicit in the phrasing. It does not contradict annotations.

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 sentences, zero filler. The primary purpose and default behavior are front-loaded, and the source attribution is neatly appended. Every sentence earns its place.

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 simple, single-optional-parameter utility, the description fully covers what an agent needs: what it counts, the target date, the default and optional input, and the format. An output schema exists to handle return-value details, and annotations cover safety. Nothing critical is missing.

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%, with the 'from' parameter already documented as 'Optional date to count from, in YYYY-MM-DD format (defaults to today)'. The description's mention of an optional 'from' date in the same format adds no additional semantic value beyond what the schema provides, so the baseline score of 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 names a precise verb ('Count') and an unambiguous resource ('the number of sleeps until the next Christmas Day'), with the date specified as 25 December. This makes it immediately distinguishable from generic date utilities like hopi_date_calculator or hopi_days_between_dates.

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 clearly explains the default behavior (uses today's date) and the optional 'from' date, giving enough context to know when to invoke the tool. It doesn't explicitly name alternatives or exclusions, but the narrow Christmas-only scope makes misuse unlikely, so the context is clear without explicit sibling comparison.

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