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

Annotations already establish the safe-read profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description still adds real behavioral context: exactly which holidays are/aren't covered, that Sunday is excluded by the weekday baseline, the step-wise algorithm, and a REST fallback endpoint. It stops short of stating bounds enforcement or error behavior.

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?

Well front-loaded and sectioned (usage, what-it-computes, inputs, outputs, formula, fallback, docs), with each block earning its place except the redundant repeated 'Inputs'/'Outputs' restatement and the awkward example-request fragment 'around Midsummer Eve is not statutory.' Still efficient and easy to scan.

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?

With an output schema present the return contract needs no exposition, and annotations cover safety, so the description's job is mostly scope and routing — both addressed via the coverage statement and exclusion list. The only substantive gap is the malformed when-not sentence, which weakens an otherwise complete definition.

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% (signed offset semantics, 2026-2027 date range, +/-1000 bounds all live in the schema), so the baseline is 3. The description only restates the inputs as 'start_date (date); working_days (integer)' and adds no meaning beyond what the schema already provides.

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 specific verb and resource: 'Adds or subtracts Sweden authority-scope working days,' which clearly differentiates it from the many sibling add_*_working_days tools by territory. It never explicitly contrasts with the closely-named siblings check_se_working_day or count_se_working_days, so the boundary against those is left to inference.

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 a positive trigger ('when you need a deterministic Sweden working-day offset... return its calculation instead of answering from memory') and a negative scope ('Midsummer Eve, Christmas Eve... employer, collective-agreement, sector, school... closures are not inferred'). The 'Do not use this when nationwide statutory list only' fragment is syntactically broken and hard to act on, but the surrounding exclusion list carries the guidance.

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