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

Annotations already cover read-only and non-mutating behavior. The description adds a useful value-format caveat for later pre-filling, but does not disclose any additional behavioral traits of this operation beyond what the annotations imply.

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, purposeful sentences. The core action and timing are front-loaded, and the value-format warning is compact and relevant.

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 the simple read-only nature and the lack of an output schema, it communicates what is returned ('all form fields') and why the agent should use it. It does not spell out the exact return structure, but the purpose is clear.

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 already explains fileId as the uploaded file identifier. The description reinforces that it refers to an uploaded PDF, but does not add substantial meaning beyond the input schema.

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 ('Retrieve all form fields'), the resource ('a PDF file'), and the stage in the workflow ('before creating a document from it'). This distinguishes it from related field/pre-fill operations.

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?

Explicitly tells the agent when to call this function: after upload_file and before document creation. It could name alternatives or conditions where it should not be used, but the workflow context is solid.

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