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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false, but the description adds important context beyond them: it describes the full returned document, states the not-found failure mode, and notes the Cotlet API key access requirement. This is rich behavioral disclosure that the annotations alone do not provide.

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?

The first sentence already lists 'lines, taxes, totals, series, folio and UUID,' and the second sentence repeats 'lines, tax per line, totals, series, folio and the UUID' almost verbatim. That redundancy wastes space, though the description is still front-loaded and generally readable.

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?

For a one-parameter read tool with no output schema, the description explains what is returned, the failure case, the authentication need, and the intended usage before credit/cancel operations. Nothing essential for correct invocation is missing.

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% and the single parameter is documented as 'Invoice ID from list_invoices or create_invoice.' The description adds no further syntax or format detail for invoice_id, so the baseline 3 is appropriate.

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 verb ('Get') and resource ('invoice or credit note') and scopes it to a single document, distinguishing it from list_invoices and create/credit-note siblings. It names the returned fields (lines, taxes, totals, series, folio, UUID) and explicitly frames it as the read used before a credit note or cancellation.

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?

It gives a clear usage scenario: 'Use it before a credit note or a cancellation to see what you are changing.' This tells the agent when to reach for this tool, but it does not name the alternative (list_invoices) for retrieving multiple invoices, so exclusions are absent.

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