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

Goes well beyond the readOnly/idempotent/destructive annotations: no conversion is consumed, the uploaded file is deleted as soon as the report is produced, and the size limit and the fallback to create_upload_url are spelled out. It also discloses the epistemic limits of the output (technical checks only, not a certification or tax attestation) and flags invoice content as untrusted third-party data — unusually rich disclosure for a read operation.

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 purpose and the list of checks, then the cost/cleanup behavior, then accepted sources, then caveats. Every sentence carries information, though the prompt-injection warning is wordy relative to the rest.

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 single-source-parameter tool with rich annotations and an output schema, the description covers invocation paths, limits, side effects, cost impact, and report interpretation caveats. Nothing an agent needs in order to call it or interpret the result correctly 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?

Though reported schema coverage is 0%, the description compensates by naming both source modes, the 3 MB decoded ceiling, and that upload_id comes from create_upload_url with purpose « validate », which is the key semantic link between sibling tools. It stops short of describing the report fields, but the output schema covers that.

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 ('Vérifie un PDF Factur-X existant') and enumerates the concrete checks performed (PDF/A-3, embedded XML, XSD, EN 16931 schematron, French rules, PDF/XML consistency). The word 'existant' plus 'Ne décompte AUCUNE conversion' cleanly separates it from the sibling convert_to_facturx, which produces rather than verifies files.

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 prescribes the two accepted input paths (base64 PDF up to 3 MB, or an upload_id obtained from create_upload_url with purpose « validate »), which is exactly the routing an agent needs. It does not explicitly state when to prefer this over siblings like convert_to_facturx, though 'existant' implies it.

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