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

Goes well beyond the readOnly/idempotent/non-destructive annotations: 10 MB size cap, 25 s runtime, refusal of encrypted files, price of USD 0.01 with no free tier, 'failures not charged', and an explicit prompt-injection warning about returned page text and on-chain strings. These are exactly the operational facts an agent needs before calling a paid, closed-world tool.

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?

Front-loads purpose then packs limits, cost and safety in short clauses with zero filler. Some fragments are garbled ('Returns runs PDF/UA-1 or PDF/UA-2 machine checks') and read as compressed notes rather than clean prose.

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 an output schema present, the description need not explain return structure, and it still summarizes what comes back (rule, page and object evidence, fix hints, unperformed manual checks) while covering cost, limits, encryption refusal and untrusted-input handling. Nothing an agent needs to call it correctly 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%, so both parameters (standard, file_base64) are already documented with enum values and size bounds. The description only restates that ua1/ua2 correspond to PDF/UA-1/PDF/UA-2 and adds no format or encoding guidance beyond the schema, so the baseline applies.

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 ('Check a PDF against PDF/UA machine rules') and names the two standards (PDF/UA-1/UA-2, veraPDF) plus the input contract (one inline PDF). It does not differentiate itself from the nearby sibling validate_pdf_a, which an agent could easily confuse with this tool.

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?

Adds a useful scope exclusion ('Not a full review or legal compliance finding') and a hard precondition ('Encrypted PDFs refused'), but never names an alternative tool or says which situations should route elsewhere (e.g. validate_pdf_a). Usage is implied rather than directed.

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