Stamp text on a PDF

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

With no annotations provided, the description carries the disclosure burden and handles the main safety trait well: it writes a new file and leaves input untouched. It also reveals the free-tier restriction on PAID/DRAFT presets. It does not mention overwrite consequences or billing behaviour for custom text, though the schema partially covers those.

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 short sentences, with the core action front-loaded and no filler. The free-tier sentence earns its place because it changes how the caller should pick text.

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 9-parameter tool with no annotations and no output schema, the description covers the primary use case and the key non-destructive behaviour, while the schema documents all parameters. It could be more complete about return values and what happens when overwrite is false, but the high schema coverage keeps it sufficient.

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?

Parameter coverage in the schema is 100%, so the description only needs to add non-schema context. It adds useful framing around text presets and colours, but largely restates what the text/colour parameter descriptions already say. Baseline 3 is appropriate.

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 concrete action: draw a word such as PAID or DRAFT on PDF pages with chosen colour and position. It clearly identifies the resource and operation, but it does not explicitly differentiate it from the similar sibling pdf_watermark_business, so it misses the top bar.

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?

"Call this tool to draw..." gives a direct use context, and the free-tier note tells the agent when preset behaviour applies. It does not state exclusions or name alternatives such as pdf_watermark_business, so it is clear but not fully routed.

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