Probe a document

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds critical behavioral context beyond those hints: it does not extract, render, run macros, follow external references, or open a network connection; it handles legacy formats; it can hit resource limits (referenced by 'Raise after a BUDGET_EXCEEDED error'). This is exactly the kind of non-obvious behavior an agent needs to trust the tool with untrusted files.

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?

The description is well-structured: opening scope sentence, format list, usage hint, and a final 'does not' sentence. It is front-loaded with the core purpose and scoping. It earns its sentences; only a minor redundancy exists (the 'Prefer this over...' sentence partially repeats the 'does not' list). Not a 5, but far above the typical terse definition.

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?

For a tool with 7 parameters, nested budget object, output schema present, and complex behavior (format drivers, confidence levels, presets, resource limits), the description provides substantial orientation: preset suggestions, the @summary caveat, the budget-error hint, and a clear non-extraction guarantee. The description does not explain what each target means, but it correctly defers to list_targets. So it's complete enough without being exhaustive.

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 the schema already documents all 7 parameters well. The description adds important cross-references that the schema alone does not capture: the distinction between @summary and full-read statistics, the warning that @summary omits page_count so ask explicitly, and that list_targets should be used rather than guessing names. This goes beyond a baseline 3 by explaining how the parameters interact with presets and the driver's default set.

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?

The description opens with a specific verb ('Read facts about one local PDF, Microsoft Office, or Apple iWork document') plus a precise resource list (page/slide/sheet counts, title/author/dates, encryption, macros, structure, assets, integrity). The scope is explicit: it reports facts ABOUT the document, never extracts text, renders, runs macros, or opens connections. It also names sibling tools (list_targets, probe_batch) and distinguishes from unzipping/byte-parsing by hand. This is clear and differentiated.

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 description explicitly advises 'Start with targets ["@summary"], or ["@security"] to triage an untrusted file.' and 'Prefer this over unzipping the document or parsing its bytes by hand.' It also warns about @summary omitting statistics and instructs to 'Call list_targets rather than guessing a name.' This provides direct when-to-use and when-not-to-use guidance, plus pointers to alternatives.

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