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

Annotations already declare readOnly, idempotent, non-destructive, non-open-world, so the safety profile is covered. The description adds real behavioral context beyond them: results are paginated with one page per call, and totals over the whole set require summarize.all_pages — a mistake-prone detail worth stating.

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?

Three short sentences with zero waste: purpose first, upstream reference second, the pagination caveat last. Nothing is repeated from the schema or annotations.

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, so return values need not be explained, and the schema carries the filter semantics for 23 params. The description supplies the docs link and the pagination aggregation caveat, leaving only sibling disambiguation as a gap.

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 87%, so the baseline is 3 and the 23 filter params are documented in the schema itself. The description still adds value by explaining the cross-page semantics of summarize.all_pages ('totals over every page') and implying page/limit pagination, which the schema does not spell out.

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?

Uses a specific verb+resource ('Retrieve a list of supplier invoices') and pins the upstream endpoint (Fortnox GET /3/supplierinvoices), so the agent knows exactly what data comes back. It does not differentiate itself from the close sibling find_supplier_invoices, which is the main ambiguity left.

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?

Use is implied by the resource name and by the pagination note, and it usefully says to reach for summarize.all_pages when totals across pages are needed. But there is no explicit when/when-not guidance and no pointer to alternatives such as find_supplier_invoices or get_supplier_invoice for a single record.

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