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

Annotations already declare that the tool is non-read-only, non-destructive, non-idempotent, and closed-world. The description adds useful behavior beyond annotations by naming accepted image formats, the default placement, and the top-left coordinate origin, but it does not clarify whether the original PDF is modified or a new signed file is created.

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. It conveys the core action, supported image formats, default placement, and coordinate system efficiently.

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 tool has 12 parameters, nested file and signature objects, and only 50% schema description coverage. The output schema and annotations reduce the burden, but the description still does not explain the multiple input routes for the PDF and signature or the page/width options, leaving meaningful gaps for a complex mutation tool.

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 50%, and the description usefully explains placement semantics for position and x/y, including the default bottom-right and points measured from the top-left. However, many of the 12 parameters—such as file/file_id/file_url, library_file_id, signature_url, signature_file_id, and width—are not addressed, so the description only partially compensates for the coverage gap.

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 states a specific verb, 'Stamp,' and resource, 'a signature image ... on a page,' including supported formats and placement modes. It clearly distinguishes this from generic PDF editing, though it does not explicitly differentiate itself from the sibling stamp_pdf tool.

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?

There is no explicit guidance on when to use this tool versus alternatives such as stamp_pdf or smart_edit. The signing use case is implied by the verb and resource, but the agent must infer when this tool is the right choice.

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