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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the trailing 'Read-only.' restates structured data rather than adding to it. The only added value is disclosing what categories of data the response contains, which is partially redundant with the 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?

Single front-loaded sentence that leads with the verb and the resource, followed by a short qualifier. The 'Read-only.' fragment is the one sentence that does not earn its place, since annotations cover it.

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?

Zero-parameter tool with an output schema and rich annotations; the description covers the domain of results well enough that an agent knows exactly what it is asking for. Nothing needed to invoke it 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?

The tool takes zero parameters, so the baseline is 4; there is nothing parameter-wise the description could clarify that the empty schema does not. No incorrect or missing parameter discussion.

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 ('Lists') and resource ('screenshot export formats'), then enumerates the exact facets returned (device families, platforms, authored dimensions, resolution presets). This is far more concrete than a sibling like get_capabilities, though it never names which sibling it complements.

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?

No explicit when-to-use or when-not-to-use statement, and no prerequisite framing such as 'call before render_screenshots to discover valid dimensions'. Usage is only implied by the enumerable contents, so an agent must infer that this is a discovery/reference call.

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