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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered structurally (the readOnly hint is arguably odd for a stamping operation, but since it transforms the supplied base64 and touches no external state it is defensible rather than contradictory). The description adds nothing behavioral beyond that — no statement that the result is a new PDF returned as base64, no note that the source file is untouched. "client and server side from freedailypro" contributes no operational context.

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?

It is a single short sentence with the action front-loaded, which is efficient. However, the trailing "client and server side from freedailypro" earns no place and consumes attention in an otherwise tight definition.

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 no output schema and 8 parameters, the description should at minimum state what comes back (a modified PDF as base64) and confirm the input file is not mutated. It says neither, leaving the agent to guess at the contract for a non-trivial multi-parameter 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 only 13% — just pageRange is documented inline — across 8 parameters, so the description carries a heavy burden and supplies nothing. Names like fontSize, startAt, skipFirstPage and the position/format enums are largely self-explanatory, which keeps this above a 1, but the agent gets no guidance on prefix usage with format=prefixed or how pageRange interacts with startAt.

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 core phrase "Add page numbers to a PDF" is a specific verb+resource an agent can act on. But the appended clause "client and server side from freedailypro" is vendor noise that neither clarifies scope nor distinguishes this from siblings like pdf_watermark or pdf_rotate. Purpose is recognizable but muddied.

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 when-to-use guidance, no prerequisites, and no mention of alternatives such as pdf_watermark (also a stamping tool) or pdf_organize. The agent must infer that this is the stamping tool from the name alone.

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