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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: the index under-reports so counts are a floor, the $0.02/call x402-on-Base pricing, the prepaid x-credit-token option for unlimited calls, the 1 free call/day allowance, and that no API key is needed. These are exactly the auth/cost/accuracy caveats an agent needs.

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 purpose is front-loaded before pricing and caveats, and the dense single paragraph is mostly substantive. A few phrases ('real usage not a guess', 'Not financial advice') are padding, and the em-dash-heavy packing makes it slightly harder to scan.

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?

An output schema exists so return values need no explanation, and the description still covers purpose, cost, authentication, and the index's known under-reporting limitation. Nothing an agent needs in order to call it correctly is missing.

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%, so both parameters are already documented in the schema. The description restates 'pass payTo to scope to one seller' and 'required input: query', adding only marginal value over the structured fields. 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?

States a specific verb and resource ('reads the CDP discovery index for a capability keyword') and enumerates exactly what it reports: match counts, distinct sellers, price range, networks, and 30-day demand metrics. An agent can distinguish it from the similarly-named x402_seller_check without opening either 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?

Names the audience and decision context ('for a builder choosing what to ship or an agent picking a provider'), which tells the agent when this tool is appropriate. It stops short of naming the alternative (e.g. x402_seller_check) or stating when-not to use it, so it lacks explicit routing guidance.

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