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

The readOnlyHint/openWorldHint annotations already cover the safety profile, yet the description adds substantial behavior: the check is free and public, returns only US listing facts, excludes Google Play, is capped at one full run per account, and the one result per product is shared for 24 hours. Those quota, regional and retention details are exactly the context annotations cannot carry.

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?

The purpose and scope are front-loaded in the first clause, followed by the alternative path and caveats. It is information-dense rather than padded, though the aside about the full check's contents ('ranks for five searches, what ChatGPT names, a subtitle to try') is more than this tool needs to be callable.

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 one parameter, no output schema, and no nesting, the description is complete: it spells out what comes back for each input type (US listing facts, or what the home page shows search engines and whether it links to the App Store), so no return-value guessing is required. The unsupported-platform note closes the remaining ambiguity.

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?

There is a single parameter with 100 percent schema description coverage, and the schema already says 'App Store link or id, or a website domain or URL'. The description restates the accepted inputs (link or id, domain) without adding format, normalization, or error-handling detail, so the baseline of 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 a specific verb and resource: 'a free public read of an App Store app (its link or id) or a website (its domain)', and immediately scopes it by naming the data returned. It also distinguishes itself from the sibling start_sign_up, which is required for the 'full check', so an agent can pick between them without opening either 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 a clear exclusion ('Google Play is not supported') and names the alternative path (start_sign_up, then run the full check from the returned page) along with the once-per-account limit that selects it. It stops short of an explicit 'use this when you only need a quick free preview' directive, but the routing is easy to infer from the contrast drawn.

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