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

Goes well beyond the annotations: quota is consumed per successful conversion exactly as on the site, an idempotency_key replay costs nothing, downloads are signed for 15 minutes single-use, and it warns that invoice content is untrusted third-party data that must not be followed as instructions. That is exactly the side-effect and security context the annotations can't 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?

Front-loaded with the outcome and return values, then progressively narrower constraints. It is a single dense paragraph and could be broken into bullets, but almost every clause (quota, idempotency, needs_input, injection warning) carries real decision value.

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 3-param tool with a deep nested schema and an output schema, the description covers the operational lifecycle (submit, resume, quota, downloads) without re-documenting return values. Omissions are minor: legal acceptance via accept_terms and the create_upload_url handoff are only partially surfaced.

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?

With 67% schema coverage, the description usefully explains the four mutually exclusive `source` variants (base64 file, upload_id, structured invoice with no AI reading, or resuming a conversion_id) and the 3 Mo ceiling. It says nothing about accept_terms beyond the schema's own text, so it does not fully cover the remaining third.

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 precise verb+resource+standard: "Convertit UNE facture en PDF Factur-X (EN 16931)" and immediately enumerates the outputs (état, rapport de contrôle, quota restant, liens signés). The capitalized "UNE" distinguishes it from the batch_convert sibling without naming it.

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?

Explicitly routes the agent: use create_upload_url for files over 3 Mo, use update_conversion when status is needs_input, and the payment link on quota_exceeded is human-only. It never says when to prefer batch_convert over this tool, so the sibling boundary is only implied by "UNE".

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