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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds substantial extra context: the exact holiday set, the weekday baseline, substitute-day non-inference, coverage years, output fields, formula, and fallback endpoint.

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?

The description is front-loaded with use and do-not-use guidance, then structured into computation, example, inputs, outputs, formula, and fallback sections. It is longer than necessary for a one-parameter check tool, and the output list partially duplicates the output schema, but every section is readable and largely purposeful.

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?

Given the low complexity, high schema coverage, rich annotations, and existing output schema, the description is more than complete. It covers scope, exclusions, formula, coverage period, substitute-day policy, and invocation details.

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 schema already defines the single date parameter with format and examples. The description adds only 'Inputs: date (date)' and repeats the JSON example, so it does not meaningfully extend parameter semantics beyond the structured schema.

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 states a specific verb and resource — checking a date against Canada federal general holidays — and explicitly distinguishes this scope from provincial, municipal, private-employer, exchange, and schedule-specific calendars. The 'What it computes' section makes the calculation boundary clear.

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?

It gives explicit positive guidance ('Call this tool directly') and explicit exclusions ('Do not use this when...'), naming the alternative scopes to avoid. It also supplies a direct REST fallback path and docs URL, covering invocation paths.

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