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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new operational context: a 7-day SERP freshness window, cursor pagination with a default page size of 50, and an Indie-plan requirement with trial counting. It stops short of explaining ordering or how the gap marker affects result filtering.

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 tight sentences, front-loaded with what the tool returns before moving to the gap-analysis option and then pagination/plan constraints. Dense but every clause carries information; only the parenthetical plan note feels slightly appended.

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 carries the return-value burden (per-keyword difficulty and popularity, plus optional own-app rank and gap markers) and notes pagination and the plan gate. The one gap is not clarifying what 'tracked' implies upstream (a sonar_track_competitor dependency), though the schema covers the ID source.

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 the baseline is 3, but the description adds meaning the schema lacks: the literal gap marker value ('gap=missing') and the concrete default page size of 50. The cursor/limit mechanics add nothing beyond the schema, leaving this just above baseline.

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 precise verb+resource: keywords a tracked competitor currently ranks for, scoped to the last 7 days of SERP data, with the returned metrics named (difficulty, popularity). That framing clearly separates it from own-app siblings like sonar_app_keywords or sonar_app_rankings without needing to open 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?

It gives a conditional usage pattern ('Pass own_app_id for gap analysis') and states the plan prerequisite, which is real guidance, but it never names an alternative tool or an explicit when-not-to-use condition. Usage is implied by the competitor-scoping rather than routed against siblings.

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