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

Annotations already cover read-only, idempotent, non-destructive, and closed-world, so the bar is low, yet the description still adds real value: it states that it produces no new file, returns facts only, and explicitly disclaims text reading, OCR, and file modification. That negative capability disclosure is exactly what an agent needs to avoid assuming 'inspect' means content extraction.

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?

A single front-loaded paragraph opens with the usage trigger, then lists the returned facts, then the scope boundaries. Every clause carries information; there is no filler or repetition of the title.

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?

An output schema exists, so return-value detail is unnecessary, and the description already signals the shape of the result ('returns these facts with no new file'). For a one-parameter read-only inspection tool with full annotation coverage, nothing an agent needs in order 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?

There is only one parameter and its nested schema is fully documented at 100% coverage. The description adds a small amount of meaning by framing it as 'one attached PDF', implying the file must already be present in the conversation, but otherwise leaves parameter detail to the schema.

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 names a specific verb (inspect) and resource (a PDF) and then enumerates exactly the facts returned: page count, page sizes such as Letter/A4/landscape, rotated or cropped pages, password protection, form fields, and selectable text. This is far more specific than the title and makes it clearly distinguishable from merge_pdfs and split_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?

It gives an explicit trigger ('Use this when the user wants to know how many pages...') and positions itself upstream of merging or splitting, which covers the when-to-use case well. It stops short of explicitly routing to a sibling tool for the actual merge/split operation, but the exclusions ('does not read or summarize the text, does not run OCR') prevent the most likely misuse.

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