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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds real value beyond them: the shape of each returned record, the Vraagposten/Te controleren workflow behavior, and the required Cotlet API key scope. That auth requirement in particular is context the annotations cannot express.

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 sentences, front-loaded with the verb and resource, each carrying distinct information (scope, return shape, domain rule, auth). The Vraagposten sentence is arguably tangential but earns its place by clarifying the unprocessed flag.

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?

No output schema exists, so the description correctly describes return fields (supplier, date, amount, status, ledger account) and the auth prerequisite; pagination is handled by limit/cursor in the schema. Complete enough to invoke correctly, with only the missing sibling cross-reference 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 100%, so the baseline is 3, but the description goes further by explaining what "unprocessed" actually means (a purchase parked on the temporary Vraagposten account that stays Te controleren), giving business meaning to the only_unprocessed flag beyond the schema's one-line definition.

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?

States a specific verb and resource ("Lists purchase invoices and receipts from Inkopen"), which cleanly separates it from the sibling snelstart_list_sales_invoices and snelstart_upload_purchase_document. However, it never names those siblings to help the agent arbitrate between them, so it stops short of full sibling differentiation.

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 phrase "optionally only unprocessed ones" implies the filter's purpose and the domain note hints at why one would chase unprocessed items, but there is no explicit when-to-use, when-not-to-use, or named alternative tool. Usage is left to inference from the resource name.

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