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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description goes further by disclosing the quota (10 free calls/day), the cost after that ($0.001/call) and both auth paths (x402 payment via params._meta or X-API-Key credits) — genuinely actionable invocation context that annotations cannot convey.

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?

The capability statement is front-loaded in one dense sentence, followed by the concise pricing/auth block. The trailing '[served by tools.moneytools.dev]' is low-value filler, and the payment clause is compressed enough to require a second read.

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 single-parameter read-only checker with an output schema, the important gaps are covered: what it detects, the cost/quota, and how to authenticate. Nothing critical is missing, though a hint about what the verdict contains (beyond the output schema) and any input-format caveats would round it out.

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?

There is one parameter with 100% schema description coverage ('domain or URL' plus a punycode example), so the schema already does the work. The description only implicitly confirms that punycode/URL forms are acceptable; it adds no format rules such as whether a full URL with path is tolerated.

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?

Names specific operations (punycode decoding, mixed-script detection, look-alike characters, one-letter brand/wallet typos) with a concrete example (Cyrillic а vs Latin a), so the agent knows exactly what signal it returns. This is clearly distinct from registration/DNS siblings like domain_rdap or robots_check.

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 phrase 'Anti-phishing for agents' implies the use case but never states when to prefer this over a sibling, nor any exclusions (e.g., that it does not check registration age or reputation). Usage must be inferred from the purpose statement alone.

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