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 safety profile is covered. The description still adds non-obvious behavior: no API key is required, results are ordered, and the returned markdown images are intended for vision-model inspection — genuinely useful context beyond the annotations.

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?

Four short sentences, front-loaded with what the tool returns, then localization, then index semantics, then the auth fact. Each sentence carries distinct information with no filler or repetition.

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 does the work of explaining the return content (ordered screenshots plus markdown images). It covers the three parameters and the no-auth fact. Minor gaps remain around out-of-range index behavior or empty-listing behavior, but nothing essential for correct invocation 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?

Schema coverage is 100%, so a 3 is the baseline, but the description adds meaning the schema does not: index is 1-based and matches the /apps/:slug/screens/:index route. It restates the country examples already in the schema, which is redundant but harmless.

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 ('Get the ordered App Store listing screenshots for a library app') and describes the payload shape (markdown images a vision model can inspect). It does not explicitly distinguish itself from the sibling get_screenshots or get_directory_app, so sibling differentiation is only implied by the 'directory' framing.

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?

Gives clear context for the country parameter ('Pass country ... for the localized listing in that storefront') and cross-references get_directory_app for storefront discovery. There is no explicit statement of when NOT to use this tool versus get_screenshots, but the usage context is clear.

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