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

Annotations already mark it readOnly/non-destructive, and the description reinforces this with 'Free; changes nothing.' It adds that the return is a 'small copy' (low-res preview), which is behavioral context the annotations lack. It does not explain format, dimensions, or failure behavior, keeping it short of a 5.

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-loads the core action and the video caveat, then usage and output expectations. The final branding/IP sentence is somewhat tangential to tool invocation but is a single efficient sentence, so overall structure holds up.

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?

Covers what the tool is, when to use it, the video-frame limitation, return nature (small copy), and that it is free/side-effect-free. No output schema exists, so the bit about the return preview is appropriately included; failure modes and exact output type are unstated but minor for a read operation.

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 100%, and the schema itself documents the id format including the 'upload:<r2Path>' variant. The description adds no further param detail, so the baseline 3 applies.

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 the specific verb ('look at') and resource ('one of the user's Pixly photos or videos'), and immediately clarifies the video edge case (a video gives its first frame). This distinguishes it from production siblings like enhance_photo or photo_to_video, which transform rather than view.

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?

Explicitly says to use it 'before writing anything about a Pixly result: a caption, a listing description, what changed,' and warns 'You cannot see Pixly results otherwise.' This gives both when-to-use and the consequence of skipping it, which no sibling provides.

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