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

Annotations already cover safety (readOnly, idempotent, non-destructive), but the description adds real operational context the annotations cannot: works without an API key on a per-IP free tier, Apple search results are capped at the top 50 and cached up to 30 minutes, editorial cards are excluded, and throttling can return a stored copy surfaced as `{ data, meta }` with `meta.stale`, `meta.stale_as_of` and a note to relay to the user. That is a meaningful disclosure of degraded-state behavior beyond schema and annotations.

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 core action and the main use case in the first clause, then the return shape, then the source semantics. It is dense and long for a single paragraph, and the per-source taxonomy of `app_store` / `itunes_search` / `google_play` is verbose, but each of those details prevents a concrete reporting error, so little is genuinely wasteful.

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?

There is no output schema, so the description carries the return-value burden alone — and it does: it names the `{ source, data }` envelope, the compact field set, the `rank` semantics per source, and the alternate `{ data, meta }` stale response shape. Combined with auth and freshness notes, an agent has everything needed to call this and interpret the result.

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 every parameter (query, store, num, fields, country) is already documented there, including the compact-vs-full field list. The description restates the compact default and the `fields: "full"` option without adding syntax or format detail beyond the schema. Baseline 3 is appropriate since the schema does the heavy lifting.

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 ("Find apps in the App Store or Google Play by keyword") and immediately names its purpose in the workflow (get a store ID before calling other tools). It also distinguishes itself from sonar_app_lookup and sonar_track_keywords, so an agent can route correctly without opening a 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?

Explicit when-to-use is given (resolve keyword to store ID; one-off snapshot of a position), plus when-not-to-use alternatives: sonar_app_lookup for one app's full details, sonar_track_keywords + sonar_app_rankings/sonar_keyword_rankings for rank history, daily tracking, or positions beyond 50. It also warns which output must never be reported as a rank.

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