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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the result is computed server-side from live Fortnox data and covers all pages, meaning the agent gets a complete reconciliation rather than a paginated slice. Minor gap: it does not say how months with no payroll activity are handled.

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 compact sentences lead with the check itself, followed by example questions and the data-provenance note. Nothing is padding, though the Fortnox API URL is marginally gratuitous for an agent that cannot call it.

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, return values need not be explained, and all three optional parameters are fully described in-schema. The remaining shortfall is that the entire definition is Swedish-only, and there is no note on what happens when the period contains no booked payroll or on how the from/to defaults are derived when a fiscal year is ambiguous.

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 from/to/date defaults (previous month, first month of the fiscal year) and formats are already fully documented in the schema. The description only implies month-by-month scope via "månad för månad" and adds no syntax, range, or precedence details beyond what the schema states. 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 check with a specific object: whether employer contributions (arbetsgivaravgifter) and withheld tax match booked salaries month by month, plus whether the tax/contribution liabilities are paid. That is far more informative than the title alone. It does not, however, explicitly position itself against adjacent siblings such as check_vat or get_personnel_costs, so an agent must infer the boundary from domain wording.

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 embedded example questions ("Stämmer arbetsgivaravgifterna mot lönerna? Är personalskatten betald?") give concrete situations that should trigger this tool, which is real usage context rather than tautology. There are no explicit exclusions or named alternative tools for overlapping cases, so it falls short of full when/when-not guidance.

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