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

Annotations already declare readOnlyHint and openWorldHint, but the description adds real value beyond them: the exact data source (public page JSON-LD block), the excluded data fields, and the charging model ($0.002 in USDC per successful call via x402, failed calls free). It omits freshness/caching and failure behavior details, so not a 5.

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 dense sentences: what is returned first, what is not returned second, cost third. Zero filler and the most decision-relevant facts are front-loaded.

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?

An output schema exists so return structure needn't be explained, and the description covers source, field scope, exclusions and pricing. Only minor operational details (data freshness, error semantics beyond billing) are left implicit, which is acceptable for a single-parameter read tool.

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% and the schema itself supplies both the description ('Android package name') and an example (com.spotify.music). The description adds no further parameter meaning, 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?

States a specific verb and resource ('Google Play app details from the public app page's JSON-LD') and enumerates exactly which fields come back (name, developer, category, content rating, rating stats, description). This clearly separates it from store siblings like dev_apple_app_store_iphone, dev_mac_app_store and dev_shopify_app_store without needing their schemas.

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?

Explicitly bounds the tool's scope by stating that install counts and reviews 'are not on that block and are not returned', which tells the agent when this tool will not satisfy a request. It does not, however, name an alternative tool for the excluded data, leaving that routing to inference.

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