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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description still adds genuinely useful context that annotations cannot: the meaning of 'canvas dimensions' as the pixel coordinate space all layouts use, and that devices are grouped by store. It does not mention whether the list is static or paginated, which keeps it below 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?

Two sentences, zero filler. The primary content (what is listed and what each entry contains) is front-loaded, and the call-to-action comes last.

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 no output schema, the description carries the burden of describing returns, and it does so reasonably: device sizes, canvas dimensions with their coordinate meaning, and store membership. The only gap is not stating how devices are identified/named for use in sonar_create_screenshot_set.

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?

The tool takes zero parameters, so there are no argument semantics to clarify; the baseline for a parameterless tool is 4. The description correctly implies a no-argument enumeration by framing this as a catalog lookup.

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 (list screenshot devices) plus scope: device sizes supported for app-store screenshot sets, with canvas dimensions and store membership. An agent can immediately distinguish this from siblings like sonar_list_screenshot_sets or sonar_create_screenshot_set.

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 routes the agent into the workflow: 'Pick a device here before sonar_create_screenshot_set,' naming the downstream tool and the ordering constraint. No when-not guidance or mention of the layout guide alternative (sonar_screenshot_layout_guide), so it falls short of a 5.

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