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

Annotations only declare the non-read-only, non-idempotent profile; the description adds the traits that actually matter operationally: single-use URL, 10-minute expiry, minimum 3 MB, maximum 10 MB / 10 pages, and that the upload is performed out-of-band via HTTP PUT. Those constraints are not derivable from the annotations or schema.

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?

Four sentences, front-loaded with what is created and its limits, then the mechanics, then the downstream handoff, then formats. No filler and no repetition of the tool name or title.

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 two-parameter tool with an output schema and annotations, the description covers everything an agent needs: how to obtain the URL, how to upload, size/format/expiry constraints, and what to do next. Return values are correctly left to the output schema.

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 schema already documents both fields and the purpose enum, establishing a baseline of 3. The description goes further by tying the two enum values to concrete file-format rules (conversion vs. Factur-X verification), which gives the purpose parameter real decision meaning.

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 names a specific verb and resource ("Crée une URL de téléversement à usage unique") and immediately scopes it with lifetime and size limits. It is clearly differentiated from the sibling conversion tools by framing itself as the prerequisite upload step whose upload_id feeds convert_to_facturx, batch_convert or validate_facturx.

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 states exactly what to do with the result (HTTP PUT with the given Content-Type, then pass upload_id to one of three named siblings) and gives per-purpose eligibility rules: PDF/JPG/PNG/XLSX/CSV for conversion, PDF only for validation. The exclusion "Aucune URL distante n'est acceptée" explicitly rules out an approach an agent might otherwise try.

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