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

Describes the return value but omits important behavioral details such as whether the original PDF is modified or a new file is created, how missing or invalid fields are handled, and what 'flatten' actually does. Annotations indicate non-destructive, but this is not conveyed in the description.

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 sentence with no filler. Conveys the core action, input, optional flag, and output efficiently.

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?

Within the context of many PDF tools, it distinguishes from reading but not from merging or other modifications. No output schema, so response structure is unclear. Does not mention error behavior or edge cases, making it only partially complete for an agent.

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 fully documents all three parameters. Description adds 'field -> value' for fields and 'optionally flatten' for the boolean, but does not define flatten's effect or the expected value types in the map, leaving some ambiguity.

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?

Clearly states the action (fill form fields), the input mapping (map of field -> value), optional flattening, and the return value (file_id and ~1h URL). Distinct from sibling tools like read_pdf_form which reads forms.

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?

Lacks explicit guidance on when to use this tool versus reading or editing PDFs, though the function name and description make the primary use case obvious. No mention of when to prefer read_pdf_form or other PDF tools.

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