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

Annotations already cover idempotency and non-destructiveness, and the description adds meaningful behavioral details: a 1-credit cost per call, a 15-minute valid download link, and the requirement to include that link in replies. It also discloses the format placeholder constraint. No contradictions with 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?

The description is compact and front-loaded with the core purpose. Each sentence earns its place: purpose, scope, format constraint, cost, and output handling. There is no fluff, and the most important information (what it does) appears first.

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 8 parameters (all documented in schema) and no output schema, the description provides all necessary behavioral context: cost, link validity, and the instruction to always include the link. It also covers the format placeholder rule. An agent has enough to call it correctly without ambiguity.

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 100% description coverage for all 8 parameters, so the baseline is 3. The description adds value by clarifying that the `format` must contain {n} and can use {total}, and by explaining that `pages` controls which pages get stamped. These are semantic nuances not fully captured in the schema descriptions.

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 states a specific verb ('Add'), a specific resource ('page numbers to a PDF'), and the action ('Stamps a page number on every page'). It clearly distinguishes this from sibling tools like merge_pdfs or watermark_pdf by focusing on page-number placement. The mention of the `pages` parameter further clarifies scope.

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 gives clear context on how to use the tool (format constraints, cost, and output link) but does not explicitly state when not to use it or list alternatives. The purpose is unambiguous enough that an agent can infer when to select it, but it lacks explicit exclusions or comparisons to siblings.

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