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

Goes well beyond the readOnlyHint/openWorldHint annotations by disclosing the exact request pattern (a single GET of the home page), the risky outcome interpretation (arbitrary-origin echo with credentials), and full cost mechanics: $0.002 USDC via x402 on Base/Solana/Arc, with failed calls not charged. That is precisely the operational context annotations cannot express.

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?

Four tight sentences, front-loaded with what is checked and the risky case, then scope limits, then pricing. No repetition of the tool name or title, and every clause adds decision-relevant 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?

An output schema exists, so return shape needn't be described; what remains — scope of the probe, the interpretation of a dangerous finding, and the billing model before invoking a paid tool — is all present. Nothing an agent needs to call this 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?

The single domain parameter is fully documented in the schema (100% coverage), so the baseline is 3. The description adds only the implicit notion that the domain's home page is what gets fetched, which is mild added value rather than new parameter semantics.

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 (checks how a site's home page answers a cross-origin request) and enumerates exactly what it inspects: origin echo, wildcard, and credentials. An agent can separate it from nearby siblings like security_crossdomain_xml_test or security_security_headers without reading any 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?

The description gives clear boundary conditions — one GET of the home page, no API routes, no null-origin testing — which effectively tells the agent when this tool will and won't answer a CORS question. It stops short of naming a sibling as the alternative for the excluded cases, so it lands at 4 rather than 5.

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