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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety and side effects are covered. The description adds genuinely useful behavior: amounts are 'never converted' per currency, and it explicitly says the report includes 'what was left out and why' plus a `basis` field explaining how it was counted. It does not mention pagination, size limits or response shape details, so it goes beyond annotations but not richly.

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 the resource name, but the body is a single dense sentence stuffed with em-dash parentheticals and nested qualifiers ('(Sweden: the momsdeklaration's boxes, its own invoices in)'), which slows parsing. Every clause contributes information, but the structure could be broken into shorter statements without losing content.

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 no output schema, the description must carry the return shape, and it partly does: it explains the per-currency/per-rate breakdown, `vat_return`, `basis`, and the omitted-items section. However, field names like `basis` and `vat_return` are only loosely described, and the country-specific behavior (Norway SAF-T codes, Sweden's momsdeklaration) is asserted rather than explained, leaving gaps for a report tool of this complexity.

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 coverage is 100%, so the schema already documents `from`, `to` and `merchant_id`, including the 'shop's own day' nuance. The description adds one real constraint not in the schema — the period may cover 'at most a year' — but otherwise adds no format or semantics beyond what the schema provides; baseline 3 fits.

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 resource (the «MVA-rapport» for a day range) and enumerates its content: per-currency/per-rate base and VAT of consumer sales, refunds, net, exports, and the `vat_return`. It is clearly a VAT reporting tool, though it never contrasts itself with siblings like sales_breakdown or sales_summary, leaving the agent to infer the boundary.

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?

There is no when-to-use or when-not-to-use guidance and no named alternative. The only scoping statement is the period length limit ('at most a year'), which constrains the call but does not tell an agent when this tool beats sales_breakdown or sales_by_period.

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