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

No annotations are supplied, so the description carries the full burden, and it does disclose real constraints beyond structured data: size limit, format whitelist, a hard cap of 8 images, and cover-image ordering semantics. Gaps remain on permissions, error behavior at the cap, and whether existing images are affected.

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 dense sentences with no filler; the core action and constraints come first and the content-policy note trails. Every clause carries actionable information.

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 3-parameter input-only mutation tool with no output schema and no annotations, the definition covers input constraints well but omits authorization requirements, failure modes, and any indication of what the call returns. Adequate but with clear gaps.

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 baseline is 3. The description does add meaning by implying image_url and image_base64 are alternative input modes and that the format/size rules apply to both, which the schema itself does not encode as a oneOf, but it stops short of stating mutual exclusivity explicitly.

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 and resource: 'Add a screenshot to a listing for sale'. It clearly distinguishes an image-upload action, but never differentiates itself from the sibling tool add_screenshot, leaving the agent to guess which applies.

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 concrete usage constraints (allowed formats png/jpg/webp, 5 MB cap, maximum of 8, first image is the cover, must be real screenshots). However, there is no guidance on when to prefer this over add_screenshot, nor on prerequisites such as owning the listing or what happens when the 8-image limit is already reached.

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