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

Annotations already convey readOnlyHint=true and idempotentHint=true, so the agent knows this is a safe, non-mutating, repeatable operation. The description adds the PDF/A-3 return format, but does not explain behavior around validation failures, the check parameter, or whether input XML must be schema-valid beyond what the schema description says.

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 description is a single, front-loaded sentence with no filler. Every word contributes to the core purpose and output format.

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?

The description is adequate for a straightforward embedding operation with well-covered schema parameters, but it omits usage context relative to sibling tools, the default rule set, and any caveats about input validation. It does state the key output format, but an agent might need more guidance to choose this tool confidently over generate_invoice or validate_invoice.

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%, so all parameters are already documented in the input schema. The description adds no extra parameter-level meaning beyond 'existing PDF' and 'Factur-X XML', which are already present in the schema descriptions.

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 clearly states the action (Attach/Embed), the resource (a Factur-X XML into an existing PDF), and the result (a PDF/A-3 Factur-X invoice). It is distinguishable from siblings like generate_invoice, validate_invoice, and extract_invoice, despite not naming them.

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?

The phrase 'to an existing PDF' gives clear context that this tool is for modifying/enriching an already existing PDF rather than generating a new one. However, it does not explicitly name alternatives or state when not to use it, so it falls short of a 5.

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