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

Annotations declare readOnlyHint=true, so the read-only nature is already disclosed. The description adds that the output is JSON and lists specific fields (name, type, value, options), which is useful context. However, it does not mention what happens when the PDF has no form fields or when the input is invalid, though this is acceptable given the read-only annotation and simplicity.

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 a single sentence that is clear and front-loaded with the action and target. It has no redundant words or filler, and every word earns its place.

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 simple read-only tool with one parameter and no output schema, the description and schema cover the necessary information. The only minor gap is the absence of error behavior or edge cases, but for this complexity level, it is complete enough.

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?

The schema provides a full description of the pdf parameter, including accepted formats (file_id or base64-encoded PDF). The tool description does not add any additional parameter guidance, but since schema description coverage is 100%, the baseline of 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 clearly states the tool lists a PDF's form fields, naming the fields (name, type, value, options) and output format as JSON. This distinguishes it from sibling tools like extract_pdf_text (which extracts text) and fill_pdf_form (which writes fields), making the purpose unambiguous.

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 provides no guidance on when to use this tool versus alternatives. It does not mention when to prefer this over extract_pdf_text or fill_pdf_form, nor does it specify any exclusions or context. There is no information about use cases or prerequisites, leaving the agent to infer usage.

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