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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds extra context by noting the data is refreshed monthly via DataForSEO (implying possible staleness) and lists the specific data components returned. This goes beyond the structured 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 a single sentence that front-loads the action and resource, followed by a compact enumeration of data points and a useful parenthetical about data freshness. It is efficient with no filler; the length is justified by the amount of specific information conveyed.

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?

For a one-parameter, read-only tool with no output schema, the description adequately communicates what the caller will receive (multiple competitor data categories). It omits potential pagination or result-limit details, but given the simplicity of the tool, the description is sufficient for correct invocation.

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?

The schema already provides full coverage for the single site_id parameter, including a clear description ('The site id, as returned by list_sites'). The tool description adds no additional meaning to the parameter, so the baseline of 3 is appropriate.

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 uses a specific verb ('List') and clearly identifies the resource ('competitors of a website') along with the precise data returned (organic keywords, estimated traffic, top counts, shared keyword positions, suggested competitors). This makes it unambiguous and easily distinguished from sibling tools like get_keywords or get_site_metrics.

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 implies when to use the tool (when you need competitive intelligence for a website) but does not explicitly contrast it with sibling tools or state when not to use it. There's no mention of alternatives or exclusions, so the guidance is implicit rather than explicit.

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