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

Annotations already establish readOnly/idempotent/non-destructive/non-open-world, so the safety bar is low. The description adds genuine value beyond them by disclosing the plan gating ('Requires an Indie plan (trial counts)') and the AI-insight condition ('if one was generated'), which the agent cannot infer from 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?

The purpose is front-loaded in the opening clause, and the parenthetical inventory of return contents is informative rather than filler. The middle sentence is long and comma-heavy, slightly taxing readability but not 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?

With no output schema, the description carries the return-value burden and does so thoroughly: it enumerates live stats, the top gap/threat/lead rows, and the optional AI insight. Combined with the plan requirement and the schema's app_id guidance, an agent has everything needed to invoke it correctly.

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 already spells out that app_id is a Sonar UUID of your own app, not a store or competitor id. The description adds nothing about the parameter, 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 concrete verb+resource: the full competitive keyword picture for one of your own apps vs every tracked competitor, and enumerates the returned stats (gaps, winnable gaps, climbers, leads). It distinguishes itself functionally ('in one call') from narrower siblings like sonar_competitor_keywords, but never names those alternatives explicitly.

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?

Provides clear usage context: 'Use it when choosing which keywords to target next.' This tells the agent the decision the tool supports, but gives no when-not guidance and does not point to alternative tools for related questions.

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