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

Beyond the readOnly/idempotent annotations, it discloses scope (worldwide App Store, last 30 days), currency semantics (gross USD before Apple's commission, no ad revenue), output shape and the meaning of each estimation method, including that rank_bound is only an upper bound. It also warns that growth fields are null until enough history exists, which is exactly the kind of caveat an agent needs.

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?

Front-loaded with the use case and trigger example, then the parameter, then the return contract; every clause carries information. The single long sentence enumerating return fields is dense but not padded.

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?

The description covers trigger, input, output semantics, estimation methods, caveats and scope limitations, so an agent can call it correctly without further inference. Since an output schema exists, the return-value detail is redundant but harmless, and nothing needed 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 description coverage is 100%, so both parameters are already documented, and the description mostly repeats the 'app id or link' guidance. The one substantive addition is reinforcing that country only locates the app while the estimate is always worldwide, which the schema also states.

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 (estimate) and specific resources (revenue and downloads) for an App Store app, so the agent knows exactly what it produces. It does not explicitly contrast itself with siblings like app_tracker_lookup, so differentiation is inferred rather than stated.

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 an explicit trigger condition ('Use this when the user asks how much an App Store app earns or how many downloads it gets') plus a concrete user-utterance example, which is strong routing guidance. It names no alternatives or exclusions, so it falls short of a 5.

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