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

With no annotations, the description carries the full burden and does well: it discloses that it costs nothing, performs no probe and no spend, and relies on stored verification signals only. It stops short of covering auth, rate limits, or failure modes, but the safety/cost profile an agent needs for a preflight tool is clear.

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?

Front-loads the key qualification (FREE, preflight, before you pay) and the field list is compact. The trailing 'Free.' repeats information already stated in the opening, which is the one wasted token.

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?

There is no output schema, so the description usefully enumerates the returned signals (registered?, payment-worthiness, confidence, coverage, reasons, evidence). Combined with the sibling contrast, an agent has enough to call it correctly, though the url parameter's expected shape remains unstated.

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 0% with a single required 'url' parameter, so the description should compensate. 'THIS endpoint' loosely implies the url is the endpoint being verified, but it never states the format or whether it accepts a bare host, full URL, or identifier, leaving the parameter essentially undocumented.

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 action (preflight check) on a specific resource (an endpoint before payment) and explicitly contrasts it with the sibling trust_check, which it calls the paid version. An agent can distinguish it from trust_check, discover, and route without opening 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?

Explicitly positions itself as the top of the funnel to use BEFORE paying and before the paid trust_check, which is named as the alternative that adds a fresh probe pass and ERC-8004 reputation. The when-to-use condition is stated directly rather than implied.

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