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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered; the description adds the credit cost (10), the paid-plan gating on advanced options, and the fact that a new downloadable file is produced rather than the original being altered. Size and page limits appear in the description as well, though they duplicate the schema. No contradiction with the read-only annotation, since the source PDF is not said to be modified.

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 core action, inputs, and return value are front-loaded in the first sentence, with plan-gated options and the cost parenthetical following. Slight redundancy in repeating the tool name at the start, but no sentence is wasted.

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?

With six optional parameters, full schema coverage, an output schema, and annotation hints, the description supplies the remaining decision-relevant facts: acceptable input forms, plan gating, credit cost, and file constraints. Nothing essential to invoking it correctly is missing, though the fallback behavior when the input exceeds the 10 MB / 300 page limits is not stated.

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 the baseline is 3; the description earns an extra point by disclosing which parameters (label format, starting number, skip cover page) are restricted to paid plans, information the schema does not carry. It also paraphrases placement as 'corner or edge' and the label as 'Page 3 of 12', which aids interpretation without contradicting the schema.

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 concrete verb and resource: it stamps a page number on every page of a PDF and returns a download link to the numbered file. That is specific enough to separate it from neighboring PDF tools such as PDFMerge, PDFtoText, and PDFtoImage without opening its schema.

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?

Gives clear operating context: the PDF may be uploaded or fetched from a public URL, placement and font size are chosen by the caller, and the label-format, start-number, and cover-skip options are gated to paid plans. It does not explicitly name a sibling tool as the alternative or state when not to use this one, which keeps it below a 5.

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