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

Annotations already declare readOnlyHint=true, so the description correctly implies no destructive behavior. It adds value by specifying the exact returned fields (difficulty, popularity, results count, autocomplete suggestions). However, it does not disclose any rate limits, authentication requirements, or potential side effects beyond what annotations provide, so a 3 is appropriate.

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?

Two concise sentences with no wasted words. The first sentence states the purpose and output, the second gives usage guidance. Every sentence earns its place.

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 adequately covers what is returned (difficulty, popularity, results count, autocomplete suggestions). It also explains the seed keyword concept. For a tool with three well-documented parameters, this is sufficient. A minor gap is not specifying the number of autocomplete suggestions or whether pagination exists, but overall it is complete enough.

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% because all three parameters have descriptions. The description adds no new parameter-specific information beyond what the schema provides; it only uses the term 'seed keyword' which matches the 'query' parameter. Baseline 3 is correct.

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 description specifies the verb 'research' and the resource 'a keyword and related terms', and lists the return values (difficulty, popularity, results count, autocomplete suggestions). This distinguishes it from sibling tools like sonar_keyword_metrics (which likely returns only metrics) and sonar_keyword_suggestions (which may return only suggestions).

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?

The description includes 'Use this to find keywords worth targeting.' which gives clear context for when to invoke the tool. However, it does not explicitly mention when NOT to use it or alternatives among the many sibling tools, so it falls short of a 5.

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