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

Annotations already cover mutability (readOnlyHint=false) and non-destructiveness (destructiveHint=false). The description adds that it 'stamps' numbers but does not disclose whether a new file is produced, whether the original is preserved, or any side effects. Minimal additional behavioral context beyond annotations.

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?

A single sentence that front-loads the main action and summarizes the important options without filler. Every word contributes to understanding the tool's purpose and capabilities.

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 6 parameters, a nested file object, and no output schema, the description is adequate but relies heavily on the schema. It does not describe the return value or explicitly state that a new PDF is produced, though the schema and annotations fill most gaps.

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 six parameters already have meaningful descriptions. The description reinforces position, start_at, and format but adds no new meaning beyond what the schema provides. Baseline of 3 is appropriate.

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 uses a specific verb ('stamp') and resource ('sequential page numbers onto a PDF'), and lists the key configuration choices (corner, starting number, format). This clearly differentiates it from the sibling add_watermark, since page numbering is a distinct operation.

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 description implies usage: you use it when you need page numbers on a PDF. However, it does not explicitly mention when to prefer this over alternatives like add_watermark, nor does it provide exclusions or conditions. Usage guidance is only implicit.

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