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

Annotations already mark the tool as idempotent and non-destructive, but the description adds genuinely useful behavior beyond that: the credit cost, the temporary download link with a 15-minute validity, and the effect of `flatten=true` making the result non-editable. This gives an agent practical expectations for side effects and outputs.

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 a one-line summary first and practical details (credit cost, link expiry) after. The first sentence partially duplicates the title and the second sentence, but the overall structure is tight and every remaining sentence contributes useful information.

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 there is no output schema, the description adequately explains the two main return behaviors: a list of fields when inspecting, and a temporary download link when filling. It also covers cost and link validity. It could mention failure modes or how the field list is structured, but for a moderate-complexity tool the essential calling context is present.

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 four parameters. The description reinforces the role of `data`, `inspect`, and `flatten`, and adds the meaningful nuance that omitting `data` triggers field listing. However, it does not add substantial syntax or formatting details beyond what the schema provides.

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 action, 'Fill a PDF form', and names the exact resource (an existing AcroForm PDF) plus the input `data`. It also clearly separates the secondary inspection mode ('or list its fields'), which distinguishes it from sibling PDF tools that merge, split, rotate, or watermark.

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 for when to use the tool: fill a PDF form with values, or list form fields when no `data` is provided / `inspect=true`. It does not explicitly name alternative sibling tools or state when not to use it, but the unique function and clear mode conditions are enough for an agent to route correctly.

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