Look up an app on the App Store

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

With readOnlyHint=true already in annotations, the safety profile is covered by structured data. The description adds two pieces of context the annotations do not: the exact data returned (since there is no output schema) and the 'Pro feature' entitlement gate. It omits country defaulting and any rate-limit behavior.

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?

Three short, front-loaded sentences with no waste. The core lookup action leads, the accepted identifier forms follow, and the terse 'Pro feature.' earns its fragment status as an entitlement gate.

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 two-parameter read-only lookup with no output schema, the description covers what the tool does, what fields come back, and how to address the app. The only real gap is that it neither explains the country parameter's effect nor distinguishes the tool from overlapping siblings.

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 both parameters (query, country) are already fully documented in the schema, including the 'us' default. The description's 'Search by name or App Store ID' merely restates the query parameter's semantics and adds nothing on country. 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?

The description states a specific verb and resource ('Look up any app on the App Store') and enumerates the return payload (ratings, reviews, version, price, category, release notes). It does not, however, differentiate itself from close siblings like app_details or list_apps, leaving an agent to guess which lookup tool to pick.

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?

It tells the agent how to address the app ('Search by name or App Store ID') and flags a gating condition ('Pro feature'), which is useful. But there is no when-to-use/when-not guidance and no pointer to app_details or list_apps, so disambiguation is left implicit.

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