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

With no annotations, the description carries the full behavioral burden and does well on the economic side: it discloses a cost of 4 credits, that billing occurs only on successful returns, and that empty results are free. That is genuinely decision-relevant context an agent cannot get from the schema. It still omits auth/permission requirements, expected latency, and failure behavior on errors, so it falls short of a 5.

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?

Two compact sentences, front-loaded with the resource and its outputs, followed by the cost terms. The output enumeration is long but each item is substantive rather than filler, so it earns its length. No boilerplate or hedging.

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?

There is no output schema, so the description must describe return values itself — and it does, listing all major data blocks including rank position and cited brands. Combined with the credit-cost disclosure, an agent has enough to invoke and interpret the call. Missing only operational details like latency, permissions, and error handling.

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% with a single parameter whose description ('A keyword or a buyer question') already defines accepted input. The description's 'For one topic' reinforces singularity but adds no format, syntax, or cardinality detail beyond the schema. Baseline 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 names a specific resource scope ('For one topic') and enumerates exactly what data comes back: search volume, CPC, difficulty, related searches, top 10 Google results, People Also Ask, and Perplexity citations. An agent knows precisely what this tool produces. It does not, however, distinguish itself from siblings like visibility or visibility_run, which also touch search performance 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?

'For one topic' implies the usage pattern — call it per keyword/buyer question rather than in bulk — but the description never states when to reach for this tool versus visibility, visibility_run, or plan. The scoping hint is useful but usage guidance is only implied, not explicit.

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