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 names the exact data sources, discloses that results are heuristic, warns it is not security advice, and states the $0.005 cost. It omits rate-limit/auth behavior but adds substantial context beyond a bare verb.

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-loaded with the core action and detection list, followed by a compact caveat and cost. Every clause earns its place with no filler.

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?

For a 1-param tool with no output schema and no annotations, the description covers inputs and methodology but says nothing about the shape of the result (score, boolean, matched-signal list), leaving the agent guessing at return semantics.

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 0% for the single 'url' parameter, so the description must compensate. It only names the resource as 'URL' without adding format or validation detail (e.g., punycode tolerance), though the lone parameter is largely self-evident.

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+resource (check a URL for phishing/scam signals) and enumerates the concrete detection methods (blocklists, RDAP domain age, punycode, HTTPS reachability). This is unmistakably distinct from the address/contract/tx inspection siblings.

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?

Usage is implied by the description — check a URL when you suspect phishing — but there is no explicit when/when-not guidance. Since no sibling overlaps in function, there is little alternative-routing to specify, so 3 is fair.

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