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

Annotations cover the read-only safety profile, and the description adds real context beyond them: the returned item fields, the pagination behavior, and the auth requirement ('Needs the user's Cotlet API key with access to this app'). This is useful behavioral disclosure.

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?

Front-loaded with the resource and search purpose, then filters, then return fields, then auth. Efficient with minimal waste, though the opening sentence is slightly redundant with the following one.

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 compensates by describing the item fields, and it notes the auth requirement. For a read-only list tool with full param coverage this is largely complete; only the relationship to sibling tools remains unaddressed.

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 the schema already documents all five parameters. The description restates the filters and paging but adds no format or syntax detail beyond what the schema provides, matching the baseline 3.

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 (list/search invoices in the administration) and the fields it returns. It is clearly distinct from mutation siblings, but it does not differentiate itself from close siblings like e-boekhouden_get_invoice or e-boekhouden_list_outstanding_invoices.

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?

Usage is implied by the filter description, but there is no explicit when-to-use guidance or exclusion versus list_outstanding_invoices or get_invoice. The agent must infer the selection criteria.

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