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

Annotations cover read-only/idempotent/open-world hints, but the description adds substantial context beyond them: free data source (Google Keyword Planner, no paid SERP calls), the critical limitation that it reports relevance never rankings, that volumes are bucketed ranges unless the Ads account has active spend, and that configured:false is a non-error state. These are exactly the behavioral traits an agent needs to avoid misusing the output.

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 dense but front-loads the core purpose first, then use case, then caveats and fallback. Almost every sentence earns its place, though the multi-clause opening sentence is slightly heavy. It stops just short of being overlong.

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 return-value burden and does so: it explains the overlap/coverage structure, the relevance-not-ranking caveat, the bucketed volume caveat, and the configured:false shape. An agent has everything needed to call it and interpret the response 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 site_id, location_code and limit_per_domain are already documented in the schema. The description adds no per-parameter syntax or defaulting details beyond that. Baseline 3 is appropriate when the schema carries the parameter burden.

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 states a specific verb and resource — the overlap between competitors' relevant keywords and the site's own terms, plus keywords the site has no coverage for. It distinguishes itself from nearby siblings like keyword_competitor_ranks and get_competitive_landscape by its relevance-overlap framing rather than ranking data.

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?

It explicitly says when to use it: 'to decide WHICH keywords deserve an exact rank check rather than checking everything.' It also provides a concrete fallback path — when Google Ads is not configured, 'just fall back to get_competitive_landscape.' Both the primary use case and the alternative are named.

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