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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the baseline is low; the description nonetheless adds the 100-result cap, the ordering ('most searched first'), and the full billing model including the $0.10 price and the no-charge conditions. The failure-billing disclosure is exactly the kind of cost/auth context annotations cannot express.

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?

Front-loaded with the resource definition, then use case, then return shape, then billing — a sensible priority order with no filler. The one blemish is redundancy: 'Not charged when the data source fails' and 'not charged if the call fails' restate billing policy twice.

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?

Despite an output schema and full annotation coverage, the description supplies the result cap, ordering, cost and failure policy — the operational facts an agent needs before calling a paid, open-world tool. Nothing material is missing for a correctly-scoped call.

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 domain, competitor and country are already documented in the schema with examples and the default. The description adds nothing about parameter meaning (e.g. whether country scopes both sites or only one), so the baseline of 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?

The description states a precise resource definition — 'up to 100 keywords a competitor ranks for on Google and your site doesn't' — which is a specific verb+resource and inherently separates it from siblings like seo_keywords or seo_rank. An agent knows exactly what set of data this returns 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?

'Use to find content ideas a competitor already proves work' gives an explicit use-case context that selects the tool for content strategy work. It stops short of naming when-not-to-use conditions or pointing to the sibling tools (seo_keywords, seo_rank) for other intents, so it is clear but not complete.

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