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

The description discloses the partial-failure behavior (provider-omitted keywords are left untouched), the credit cost and refund policy, the confirmation gate (without confirm=true it only returns cost and balance), and the subscription requirement. This goes well beyond 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 core action is front-loaded, and each subsequent sentence adds a distinct fact about side effects, cost, prerequisites, or parameter conditions. There is no redundant wording.

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 mutating, paid refresh call with four parameters, the description covers when to use it, how costs are charged/refunded, how the confirm parameter changes behavior, how website_id disambiguates accounts, and what happens to unfetchable keywords. An output schema is present, so return-value details are not needed.

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 coverage is 100%, but the description adds useful context: companion keywords must share the same website and locale, website_id is needed only when the account has several websites, and confirm controls whether the charge is acknowledged. This exceeds what the schema alone states.

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 names the exact resource and verb: it re-fetches monthly volume, difficulty, CPC, and opportunity score for one keyword plus up to 49 companion keywords of the same website and locale. It also distinguishes itself from plain getters by emphasizing it is a re-fetch that leaves missing provider keywords untouched and does not change Google Search Console positions.

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 states the trigger: use it when metrics look stale, pointing to metrics_updated_at. It also clarifies what it does not do (change GSC positions) and the prerequisite of an active subscription or free trial, though it does not name a specific alternative tool to use instead.

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