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

Adds substantial behavior beyond the annotations: it states a cost (0.05 USDC per call), the accepted payment rails, and precise error semantics (503 for unreachable, 400 for refused URL, neither charged). These are exactly the operational facts an agent needs and cannot infer from readOnlyHint/idempotentHint.

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?

Five compact sentences, front-loaded with the usage trigger and return shape, then error/cost facts. No filler; each sentence adds a distinct operational constraint.

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 not be enumerated, yet the description still summarizes them (verdict, score, 32 checks). Combined with cost, error codes, and the no-payment guarantee, nothing material is missing for a 2-parameter 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 description coverage is 100%, and the schema already explains the URL encoding constraints, host/port rules, and the method enum and its default. The description adds no parameter-level detail beyond what the schema provides, so the baseline 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 and resource ('check an x402 endpoint's payment challenge') and scopes the outcome ('verdict, a 0 to 100 score and 32 checks'). This clearly separates it from siblings like get_x402_test or get_honeypot_check without needing to open 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?

Gives explicit timing guidance: use it 'before paying' an endpoint, and clarifies it 'never pays' itself. It does not name a specific alternative sibling (e.g. get_x402_test) or state when-not to use it, so it falls short of full 5-level routing.

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