Generate store screenshots

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

Goes well beyond the bare annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false): it discloses the cost model (1 credit per set), a free-tier quota with watermarking, and the async jobId return with two retrieval paths. These are exactly the facts an agent needs before committing to a billable, non-atomic operation.

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?

Purpose is front-loaded and every clause carries information (input contract, pricing/quota, return and download path) with no filler. It is dense to the point of being packed into three long sentences, which slightly hurts scannability.

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 10-parameter, nested-object, no-output-schema tool, the description covers the essentials an agent cannot get elsewhere: credit cost, free-tier watermark limit, async jobId, and how to persist results. Combined with 100% schema coverage, nothing critical is missing for correct invocation.

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 every parameter (style, theme, targets, captions, headlines, download_to, download_format) is already documented inline, including enum meanings and ordering ties to screenshots. The description only restates the screenshots and download_to semantics, adding no new syntax or constraint detail beyond the schema, 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?

Opens with a concrete verb+resource+transform: raw app screenshots into framed App Store / Google Play marketing screenshots with headlines, plus the input contract (1–5 local paths or http(s) URLs). An agent can distinguish this from list_styles/list_devices/get_output without opening any schema.

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 operational context: one call produces one full set, set download_to to save immediately, otherwise call get_output, and free keys are capped at 3 watermarked sets per month. It does not explicitly state when NOT to use it (e.g. for non-store assets) or route to buy_credits/get_balance when credits run out, so it stops short of full when/when-not/alternatives guidance.

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