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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds useful behavioral context about high-resolution output and optional cropping, but says nothing about the return payload (image bytes vs. URL, mime type) or what happens when image_index is out of range, which matters for a tool with no output 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?

Two sentences, front-loaded with the core operation and followed by the one non-obvious detail (fractional region coordinates). No filler or redundant restatement 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?

With five parameters, one nested object, and no output schema, the description covers the operation and the trickiest parameter well. The remaining gap is the shape of the returned image (encoding, whether quality/max_px interact), which an agent must infer.

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 coverage is 80%, so the baseline is 3, but the description meaningfully adds to the hardest parameter by explaining that region values are fractions of the image and giving a concrete worked example ({x:0.5,y:0,width:0.5,height:1} for the right half). It does not add anything for max_px or quality beyond what the schema already documents.

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 ("Returns one image from a page") plus the resolution and cropping capabilities up front. An agent knows exactly what it gets, though it never distinguishes itself from the sibling onenote_download_resources or explains when an image would come from this tool vs. fetching the whole page.

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 crop rationale ("so small text in big screenshots is legible") implies when to reach for the region parameter, but there is no guidance on when to choose this tool over onenote_get_page or onenote_download_resources, and no stated prerequisites such as needing a page_id and image_index obtained from onenote_get_page.

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