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

Annotations already cover the read-only safety profile, and the description adds real behavioral context: it previews the returned payload, discloses the not-found failure mode, and states the Cotlet API key requirement. Only pagination/rate behavior is left unstated.

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 core purpose and mostly tight, but the first sentence ('One invoice with its lines, taxes, payments and client details') is largely restated by the second, creating mild redundancy.

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 competently takes on the burden of describing return contents, numbering format, error behavior, and authentication. An agent has enough to call it correctly; only edge behaviors like pagination or line limits are absent.

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 invoice_id is already fully documented as coming from list_invoices. The description adds no additional syntax or format meaning beyond the schema. 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?

States a specific verb and resource (retrieve one sales invoice) and enumerates what comes back (lines, taxes, payments, client, numbering). It is clearly distinguishable from alegra_list_invoices by the singular scope, though it never names the sibling explicitly.

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 only implied: the schema note 'Invoice ID from list_invoices' and the not-found error suggest you fetch a known ID. The description itself gives no when-to-use guidance or explicit alternative (e.g., 'use list_invoices to find the ID first').

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