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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is covered; the description adds genuinely new context by stating 'Does not use render quota,' a cost/side-effect fact not in the annotations. It does not mention behavior for non-fillable or malformed PDFs, keeping it short of a 5.

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 sentences: purpose and return shape first, the workflow link second, the quota note last. No filler and everything front-loaded.

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?

With no output schema, the description compensates by enumerating the returned fields, and the nested file parameter is fully documented in the schema. Only minor gaps remain, such as error behavior for PDFs with no form fields or protected files.

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 description coverage is 100%, including nested url/base64/password descriptions and a note to prefer url for large files, so the schema carries parameter meaning. The description adds nothing about the file parameter beyond what the schema already says, which is the baseline 3 case.

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?

States a specific verb and resource ('List a fillable PDF's form fields') and enumerates the exact fields returned (name, type, current value, options, page), which makes its output distinguishable from siblings like get_template or render_pdf.

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?

'Use the names with fill_pdf_form' positions it as the discovery step in a fill workflow and names the exact follow-up tool. It gives clear usage context but no explicit when-not-to-use or exclusion conditions.

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