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

Annotations already declare the safe read-only/idempotent profile, and the description adds genuinely non-obvious behavior: a $0.25 USDC charge per call via x402 with the payment payload location (_meta["x402/payment"]), plus the billing rule that invalid input or upstream failure errors out without being charged. Cost and payment-transport details are exactly the kind of context 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?

Two tight sentences: the batch scope and sibling relationship come first, then the cost and error/charging semantics. No filler, and the highest-value operational fact (price and payment location) is stated plainly rather than buried.

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?

With no output schema, the description should ideally hint at what comes back per item (e.g. per-item results vs. a single aggregate), and it only covers failure behavior. Coverage of cost, payment transport, limits and error charging is otherwise solid for a one-parameter read-only batch 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 coverage is 100% and the single items parameter is fully documented (1-100 strings, maxLength 260), so the baseline is 3. The description restates the same 1-100 constraint and adds only the pricing nuance that the whole batch is one flat charge, which does not extend parameter meaning beyond the schema.

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?

The description states the resource (domains or IPv4 addresses) and the batch scope (up to 100 per call), and explicitly positions itself as the batch counterpart to indicator_check. However, it never states what the check actually determines, deferring the core purpose entirely to the sibling tool's description, so it is not self-contained.

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?

"Same as indicator_check for up to 100 domains or IPv4 addresses in one call" clearly signals when to reach for this tool versus the single-item sibling, and the flat-price note gives a reason to batch. It stops short of an explicit when-not rule (e.g. what to do below the item limit or whether indicator_check is preferred for one item).

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