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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it says no file is produced, password-protected PDFs are unsupported, OCR is not run, and pages/vector drawings are not rendered as images. These are concrete negative capabilities an agent could not derive from the annotations or schema.

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-loaded with the use case, then constraints, then the anti-case; nearly every clause carries information. The middle sentence is long and bundles inputs and outputs into one run-on, which slightly hurts scanability but not clarity.

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 read-only inspection tool with a full schema and an output schema, the description covers trigger conditions, scope limits, error limits, and the alternative tool. The return fields are enumerated even though the output schema already defines them, so nothing an agent needs to call this 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 the schema already documents pages syntax, dedupe semantics, and min_width/min_height defaults. The description largely restates those (pages example, dedupe default true, minimum width/height in pixels) and never mentions the `images` parameter, so it adds only marginal meaning beyond the structured data.

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+resource plus a user-intent framing ("know which images a PDF contains, how many images are on each page, or their pixel sizes") and explicitly positions itself against the sibling by naming extract_pdf_images as the file-producing alternative.

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 states the condition that selects this tool (inspect before extracting) and the condition that excludes it ("Do not use when the user wants the image files (use extract_pdf_images)"), leaving nothing for the agent to infer.

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