keyword_metrics

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

No annotations are provided, so the description carries the full burden. It does disclose a real behavioral trait — a 0.15 USDC cost on Base via x402 — which is valuable for an agent deciding whether to call it. However, it says nothing about rate limits, caching, failure modes, or whether repeat calls are billed, and the confirmNewPurchase purchase semantics are documented only in the schema.

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?

Three tightly packed sentences, front-loaded with the capability and return fields, with the disambiguation clause and cost caveat placed after. 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 and no annotations, the description usefully names the returned fields and the billing model, which covers the biggest gaps. It falls short only on the undocumented language_code/location_code parameters and their defaults, which an agent must infer from the schema alone.

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 50%, and the description only echoes what the schema already states ('up to 1000 chosen terms'). It adds nothing for language_code or location_code, which have no descriptions in either place, so it does not compensate for the gap. Baseline 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 resource and the exact metrics returned (search volume, CPC, advertising competition, monthly history from Google Ads), and explicitly disambiguates from keyword_difficulty by noting competition is not organic SEO difficulty. An agent can tell this apart from sibling tools without opening the 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?

The disambiguation sentence ('Advertising competition is not organic SEO difficulty') gives useful negative context, but there is no explicit when-to-use guidance versus keyword_metrics_multi, keyword_ideas, or ai_search_volume, nor any stated prerequisites beyond the price hint.

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