Verify filled values are visible

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

Annotations only say read-only and non-destructive; the description adds what actually matters — that a missing binary or render error yields REFUSE with no finding rather than a false negative, and it defines the four verdict categories. The region+auto legibility rule is behavioral detail found nowhere in the structured fields.

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?

Four tight sentences, front-loaded with the mechanism, then the verdict vocabulary, then the region/auto rule, then the failure and scope caveats. No restatement of the title or padding.

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?

Output schema covers the return shape, and the description still supplies what the schema cannot: verdict meanings, failure-mode semantics (REFUSE), and the correctness-vs-legibility limit. Nothing an agent needs to invoke or interpret this tool is missing.

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 0%, so the description carries the burden; it does explain the two non-obvious params well (region accepts 'page' or fractional x0,y0,x1,y1; auto requires every text-layer word in the region to be legible). dpi and the format of values are left unexplained, and 'page' is only implied by 'Render one page'.

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 concrete verb chain (render, OCR, compare with text layer) on a specific resource (one PDF page), which no sibling does — pdf_form_fill writes, pdf_form_inspect reads metadata, pdf_sha256 hashes. The verdict taxonomy at the end makes the output shape unambiguous.

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?

The closing clause 'Proves legibility only, not correctness' gives a clear scope boundary that tells the agent when this tool's answer is not the one it needs. It never names a sibling or states a when-not-to-use case explicitly, so routing between verify/inspect/fill is left partly to inference.

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