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

Annotations already declare readOnlyHint=true, openWorldHint=true and idempotentHint=false, so the safety profile is partly covered. The description adds genuinely new behavior: it performs exactly one unpaid request, inspects the live 402 response rather than the listing metadata alone, and returns graded pass/warn/fail results with concrete fixes. It does not discuss rate limits, auth requirements, or failure modes when the endpoint is unreachable.

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?

A single front-loaded sentence opens with the audience and action, then uses a compact parenthetical list of validation targets. Dense but every listed item is substantive rather than filler; the only cost is that one long sentence demands careful parsing.

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 the return shape needn't be spelled out; the description still summarizes the pass/warn/fail outcome and that fixes are included, which is the right level. For a two-parameter, read-only diagnostic with full schema coverage, the only real gap is guidance on prerequisites (ownership of the endpoint, reachability).

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 only two parameters, both fully described in the schema (https URL; GET/POST matching the listing). The description adds no syntax, format, or constraint detail beyond that, 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?

States a specific verb (lint/check) against a specific resource (your own x402 endpoint) and names the audience ('For sellers'), plus enumerates the concrete spec facets validated (v2 header, v1 body, CAIP-2 ids, payTo, EIP-712 domain, feePayer, bazaar, CORS). This is clearly distinguishable from siblings like check_service or preflight_payment, which operate on other targets.

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 sellers' scopes the audience, and 'request an x402 endpoint once without paying and check its 402' establishes the pre-listing validation scenario. It stops short of explicit routing: it never says when to prefer this over preflight_payment or check_service, nor when not to use it (e.g., endpoints you don't own).

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