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

With no annotations, the description carries the burden. It discloses useful behavior: diagonal placement, all pages, and base64 return. It does not state whether the operation modifies the original file or returns a new watermarked PDF, which is a meaningful side-effect gap.

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 short sentence front-loads the action and output. No filler; every phrase adds information, and examples make the tool immediately understandable.

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 low-complexity tool with fully described parameters, the description is nearly complete: input and output formats are indicated and all constraints are in the schema. The only notable omission is explicit confirmation that a new file is returned rather than the original being mutated, so it is not fully complete.

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 the schema already documents all 5 parameters with types, defaults, and constraints. The description adds only example values and the 'every page' effect, which is helpful but not needed for parameter meaning.

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 uses a specific verb ('Stamp') and resource ('watermark across every page'), distinguishes the behavior (diagonal, every page) and gives concrete example text. It clearly differentiates from sibling PDF operations like splitting or merging.

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?

It conveys an implied use case: adding a label like 'CONFIDENTIAL' or 'DRAFT' to a full PDF. However, it never explicitly says when to prefer this over siblings or mentions non-use cases, so guidance remains implicit rather than explicit.

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