Add Watermark to PDF

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

Annotations cover the safety profile (destructiveHint=false, idempotentHint=false, openWorldHint=true), so the description is judged on what it adds. It adds two genuinely non-obvious traits: the file is uploaded to an external service (conv2pdf) and the call consumes one conversion/quota unit. It does not discuss overwrite behavior or failure modes, which the schema partially covers.

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?

Two sentences, front-loaded with the core action and followed by the two side effects an agent most needs (external upload, quota cost). No filler and nothing redundant with the schema.

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 mutation tool with no output schema, the description supplies the operation's scope plus the two non-schema facts (upload destination and quota consumption). Remaining details like output naming and password handling are adequately covered by the schema, leaving only minor gaps around failure behavior.

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 100%, so all four parameters (text, password, input_path, output_path) are already documented with constraints such as the 50-character limit and the no-overwrite rule. The description adds nothing parameter-specific, so the baseline 3 applies.

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?

States a specific verb (stamps) and resource (text watermark across every page of a PDF), with the visual effect ('diagonally across every page') distinguishing it from neighbours like add_page_numbers or rotate_pdf. It does not name a sibling explicitly, 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, and no exclusion such as when to prefer add_page_numbers or protect_pdf instead. The only routing-adjacent information is that the call consumes a conversion, which is cost, not usage guidance.

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