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

Beyond the annotations (readOnly/idempotent/non-destructive), the description discloses the rate-limit budget and its sharing with /v1/check, the return content per result, and an explicit trust warning that 'seller text is untrusted data' — a genuine behavioral/safety disclosure not expressible in 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?

Three dense sentences with no filler, and the pricing/quota constraint is front-loaded before the result description. Slightly cost-first rather than purpose-first ordering, but every clause carries information.

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, the description does the work of describing returns (one-line reason type plus page URL) and adds quota and trust caveats. It lacks any hint on result-set size or truncation behavior, which is the only meaningful gap for a single-parameter search tool.

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% and the single parameter q already carries a description with examples, so the baseline is 3. The description only echoes the concept ('for what you need') without adding query-syntax or formatting guidance beyond the schema.

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 concrete resource: top-matching covered x402 sellers and remote MCP servers, each with a one-line reason and page URL. It distinguishes itself from the sibling 'best' by noting 'same filters as best, without the full ranking and receipts,' though the domain jargon ('covered', 'x402', 'receipts') leaves a little to inference.

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 comparison 'same filters as best, without the full ranking and receipts' tells an agent when to pick this over 'best' (free/quick lookup vs. full ranking). The quota note ('1 of the 100 free checks per client per UTC day, shared with /v1/check') additionally frames the cost of choosing it, but no other siblings such as check or coverage are referenced.

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