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

Annotations already declare the safety profile (readOnly=true, idempotent=true, destructive=false, openWorld=false), so the bar is lower. The description adds useful non-annotation detail: the return report contents (signer, signing time, validity status, certificate-chain resolution) and that it returns the raw report. It omits auth/rate-limit context, hence not 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?

Two sentences, front-loaded with purpose and return contents, then the usage trigger. No redundant or filler phrasing; every clause earns its place.

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?

No output schema exists, but the description enumerates the report fields (signer, signing time, validity status, certificate-chain resolution), covering the return-value burden. Annotations cover the safety profile, so nothing an agent needs to invoke and 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 description coverage is 100% for the single 'file' parameter (base64-encoded bytes), so the schema carries parameter meaning by itself. The description adds nothing about the file format beyond 'of a PDF', which is the baseline-3 case when the schema does the heavy lifting.

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 (verify) and resource (embedded digital signatures of a PDF), and the parenthetical pinpoints the underlying mechanism (pdfcpu signatures validate). An agent can distinguish this cleanly from the sibling pdf_sign, which performs the opposite operation.

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 final sentence gives clear triggering context: 'Use this when the user asks whether a signed PDF is valid or who signed it.' This is a solid use-when statement, but it does not explicitly name pdf_sign/pdf_validate_pdfa as alternatives or state when NOT to use it.

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