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

Annotations only cover the safety profile (readOnly/idempotent/non-destructive/openWorld), but the description discloses the real behavioral burdens: cost (10 credits per call, refunds for uncomputed rows), auth requirements (Sonar API key or connected account, not free tier), latency (~30 seconds), and the `stale`/`pending` state semantics with their thresholds. This is well beyond what the structured fields convey.

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?

Purpose, return shape, and the sibling comparison are front-loaded and each subsequent sentence carries real information about credits, staleness, and pending behavior. It is dense and long for a 3-parameter tool, but nearly every clause earns its place; minor trimming of the pending/refund detail would tighten it.

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 full burden and does so: it enumerates the return columns, explains `measured_at`/`popularity_measured_at` as ISO 8601 UTC, defines the 7-day `stale` threshold, and explains the `pending` state. An agent has everything needed to call and interpret results 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 description coverage is 100%, so the schema already documents query, store, and country (including the 72-market constraint). The description reinforces the store/autocomplete relationship but adds no format or syntax detail beyond the schema, so the baseline of 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 specific verb+resource ("Research a keyword and related terms") and immediately defines the output: up to 10 rows, seed keyword plus top autocomplete suggestions, each with difficulty, popularity, and results count. It also explicitly distinguishes itself from sonar_keyword_metrics, so an agent can route between the two without opening either 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?

Gives explicit when-to-use guidance ("find keywords worth targeting") and names the alternative with the selecting condition ("for metrics on terms you already know, sonar_keyword_metrics is cheaper"). It further clarifies the pending/re-check handoff to sonar_keyword_metrics, leaving little to inference.

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