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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuinely useful behavior beyond them: exactly which closures are NOT inferred (Midsummer Eve, Christmas Eve, New Year's Eve, employer/collective-agreement/school/bank/local closures) and that Sunday is excluded by the weekday baseline. This pre-empts the most likely agent error on Swedish holiday semantics.

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?

It is front-loaded with when/when-not guidance, but it is bloated with a redundant per-date formula, a REST fallback URL, and a docs link, and the sentence 'Do not use this when nationwide statutory list only' is grammatically broken enough to slow reading. Content is organized but not tight.

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, yet the description also enumerates every return field, which is redundant but harmless. Combined with inputs, examples, exclusions, and scope, the definition is complete for correct invocation; the only real gap is that it never names the sibling tool an agent should use for the nationwide-statutory case.

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 four parameters are already documented, and the description essentially restates them (types and optionality) plus a complete JSON argument example. The example is mildly additive but there is no format or edge-case detail beyond the schema, so the 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 states a specific verb and resource with scope ('auditable Sweden working-day count', 'authority-scope working and non-working dates in a range'), and the scope qualifier ('authority-scope', not nationwide statutory) distinguishes it from both the add_se and check_se siblings. An agent can identify this as the range-counting tool for Sweden without opening the schema.

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 when-to-use ('auditable Sweden working-day count', return the calculation instead of answering from memory) and an exclusion ('Do not use this when nationwide statutory list only'). The exclusion is grammatically awkward and never names a concrete alternative tool, so routing is implied rather than spelled out, but the guidance is otherwise clear.

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