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

Annotations only supply destructiveHint=false, so the description carries real weight and delivers: unfilled fields keep their value, calculated fields are recomputed afterward, values render in display format, and the return payload includes file URL plus a "calculations" object. It does not mention the flatten option's irreversibility, which is the one meaningful behavioral gap.

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 tight sentences, front-loaded with purpose, then behavior, then return shape. No redundant restatement of the name or title, and every clause adds operational information.

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 correctly explains the return value (file URL and "calculations"), and covers mutation semantics and async behavior context. The only shortfall is not flagging that flatten permanently merges fields, which matters for a tool whose annotation declares nothing destructive.

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%, so baseline is 3, but the description adds meaning beyond the schema by tying the "name" parameter to its source tools and explaining display-format and calculated-field semantics of values. This is useful context the schema alone does not convey.

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 ("Fill form fields of a PDF") and explicitly names the sibling tools that supply field names ("read-pdf-form" or "visualize-pdf-form"), so an agent can distinguish it from readers and other PDF mutators. The result is also stated ("get the filled 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?

Clear context is given: field names must come from read-pdf-form or visualize-pdf-form, and unfilled fields are preserved. It stops short of explicit when-not-to-use guidance or naming alternatives like flatten/merge tools, but the workflow routing is clear enough for correct invocation.

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