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

No annotations are supplied, so the description carries the behavioral burden. It discloses useful operational details (defaults, the 6–72 font-size range, the public-URL requirement for file_url), but says nothing about whether the source file is modified, how the result is delivered, or any auth/limit constraints. With an output schema present, return values need not be explained, which keeps this at an adequate 3.

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?

One purpose line followed by five terse parameter lines, each front-loaded with the parameter name. No filler, no repetition of the schema structure.

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 single-purpose PDF mutation tool with an output schema and fully documented parameters, the definition is nearly sufficient. The remaining gap is guidance on when to choose this over watermark_pdf and whether the original file is preserved.

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 0%, so the description must compensate, and it does: it documents all five parameters, names the three allowed position values, gives the font_size range 6–72 and default 12, the start_from default of 1, and an example prefix string. This fully covers what the bare schema omits.

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 opens with a specific verb+resource: 'Добавляет номера страниц в PDF' (adds page numbers to a PDF), which is unambiguous. It does not differentiate itself from the nearest sibling watermark_pdf, which also stamps content onto pages, so it stops short of a 5.

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 (e.g. whether the PDF must be unprotected), and no mention of alternatives such as watermark_pdf for arbitrary stamps. Usage must be inferred entirely from the tool name and parameter list.

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