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

With no annotations, the description must fully disclose behavior. It only states 'Runs in the browser' and billing details, but does not explain what happens to the PDF (e.g., modifies original vs. creates new), limitations, or how the watermark is applied. This is insufficient for a tool with zero parameter 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?

The first sentence is purpose-front-loaded and clear. The billing information is somewhat lengthy but still concise overall (three sentences). Every sentence adds some context, though the pricing details could be considered less critical for immediate tool usage.

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 tool with no input schema, the description should explain how to provide a PDF and what the output will be. It lacks this and instead focuses on pricing. The 'runs in the browser' note gives minimal context, but the missing functional details leave a significant gap.

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?

The input schema has zero parameters, and schema coverage is trivially 100%, so the baseline is 4. No parameter-level detail is needed, and the description adds no parameter-specific semantics, which is acceptable.

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 'Add text watermark to PDF pages' with a specific verb and resource. This distinguishes it from sibling PDF tools like merge, split, and compress, making the purpose unambiguous.

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 purpose statement implies usage, but there is no explicit guidance on when to choose this tool over alternatives like mio_pdf_editor. The billing information addresses credits and passes, not usage context, so the tool selection guidance is only implied.

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