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

Annotations already mark the tool as read-only, open-world, and idempotent, so the additional value comes from the per-row billing, 20-row cap, 4xx/5xx non-charge disclosure, and semicolon-delimited-text response format. It adds real operational behavior without contradicting the 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 description is three compact sentences: purpose first, then billing, then response format. Each sentence earns its place and there is no filler or duplicated schema content, though the cost sentence is dense and could stand out more.

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?

Given the output schema exists and the parameter set is simple, the description covers the core purpose, cost, limits, and response format, which are the main contextual gaps. It does not address when to choose Semrush over DataForSEO alternatives, but the tool's unique resource-specific behavior is sufficiently captured.

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%, and the schema already documents the semicolon separator, 20-keyword limit, and database default. The description contributes the connection between row billing and returned data rows, but no additional parameter-level semantics beyond what the schema already conveys.

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 first sentence clearly identifies the tool as returning Semrush's keyword difficulty index, with an explicit metric scale and batch capability. It distinguishes from domain-level or competitor tools because of the specific metric and name, though it doesn't name alternative tools such as the DataForSEO bulk keyword difficulty sibling.

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 gives no scenario-based guidance such as when to choose this tool versus a sibling like post_dataforseo_labs_google_bulk_keyword_difficulty_live or get_semrush_keyword_overview. The dollar cost per row and error charging are operational context, not selection guidance.

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