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

With no annotations, the description fully carries the burden of behavioral disclosure. It reveals critical traits: all processing happens locally in the user's browser, the widget reports field names, and pre-fill is limited to user-provided data. This helps the agent understand security and workflow implications.

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 concise with two main sentences front-loading purpose and usage. A bilingual line adds minor redundancy but does not significantly detract. Every sentence adds value, but the Polish translation could be omitted for brevity.

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 no output schema, the description should explain what the tool returns or how the agent obtains the result. It mentions the widget reports field names but does not specify whether the tool returns a modified file or only opens an interactive widget. The signature parameter behavior is vague. This leaves gaps for an AI agent to infer the return value.

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%, but the description adds value beyond schema: it explains the interactive flow, that values should only contain user-provided data, and that field names are learned after load. The signature_name parameter is explained as 'handwritten-style signature,' which is already in schema but contextually reinforced.

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 fills out PDF forms using an interactive widget for AcroForm fields and flat PDFs. It distinguishes itself from siblings (merge_pdfs, sign_pdf, split_pdf) by emphasizing the interactive, local nature and specific use case.

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 states 'ALWAYS use this for PDF filling requests — never fill or regenerate the PDF yourself,' providing clear when-to-use and what-not-to-do guidance. Additionally, it explains that only explicitly provided data should be pre-filled and that the widget reports field names for user completion.

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