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

Beyond annotations, it discloses that the input file is untouched, that the output is a download link valid for one hour, that the default center position is drawn on a 45-degree diagonal, and that free tier restricts colors to preset PAID/DRAFT. These are genuinely useful behavioral traits not captured by the 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?

Three sentences, zero waste. The core purpose and key constraints are front-loaded, and each sentence carries information without redundancy.

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?

Given 9 parameters, the schema fully documents them and the description adds the critical operational details (output link expiry, free-tier limits, default diagonal). It does not mention error handling or prerequisites, but with a full schema and no output schema, this is a minor gap.

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 coverage is 100%, so baseline is 3. The description adds meaning for the 'text' parameter (preset behavior) and 'position' (diagonal default), enriching the parameter semantics slightly beyond the schema. It does not detail all params, but the schema already does that robustly.

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 ('draw'/'stamp'), a resource (PDF pages), and concrete examples (PAID, DRAFT). It clearly distinguishes this from other pdf_* tools like pdf_merge or pdf_split by focusing on stamping text across pages.

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 purpose is unmistakable, and the free-tier limitation (PAID/DRAFT presets) gives a constraint on when certain values are usable. However, it does not explicitly contrast this with the sibling pdf_watermark_business or give a 'use this when...' vs alternatives, leaving some inference to the agent.

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