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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description still adds substantial semantics: null tier/position is explained per review_status and list_ranking_status, main_list is defined as derived from the placer's primary marking and explicitly 'never guessed', and the missing_since case carries an action-level warning. This is real behavioral context an agent cannot infer from structured fields.

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?

It is front-loaded correctly — the core purpose is the first six words — and most clauses carry non-obvious semantics that would otherwise be lost without an output schema. But it is delivered as one sprawling sentence with three-deep nested parentheses, which makes the field-level rules hard to parse on a first read.

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 no output schema, the description correctly takes on the burden of explaining return-field semantics and the nullability rules that would otherwise mislead an agent. Gaps remain: what happens when the key matches nothing, and how far back 'recent history' extends, are unstated.

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 single parameter already documents 'app slug or numeric app_store_id'; the description only restates 'by slug or App Store id'. No format examples, no guidance on which key form is preferable when both exist. Baseline 3 is appropriate since the schema does the work.

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 opening clause names the exact verb and scope: 'One app by slug or App Store id', which immediately separates it from multi-app siblings like search_apps, compare_apps, and find_alternatives. It then enumerates the payload (App Store facts, generated summary, category memberships, main_list, maker claim, history), so an agent knows precisely what it retrieves.

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?

Usage is implied rather than stated: you call it when you already hold a slug or app_store_id, and the description never says how to obtain one (e.g., via search_apps) or when to prefer a sibling. The one explicit directive — do not recommend or link an app whose missing_since is set — is a genuine when-not rule, but it concerns interpreting the result rather than selecting the tool.

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