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

Beyond the readOnly/openWorld/idempotent annotations, it discloses the lookup mechanism (authoritative RDAP, DNS-delegation fallback for RDAP-less TLDs), the result taxonomy (registered/available/likely-available/unknown), extra return fields for taken names, and the full paid flow: x402 USDC on Base at $0.004 per successful call, with a PaymentRequired object if called unpaid.

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?

A single dense sentence, but the usage trigger is front-loaded and each clause carries distinct information (limit, data source, fallback, result states, pricing). The payment clause trails, which is slightly less ideal ordering for a budget-constrained agent, but nothing is wasted.

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?

No output schema exists, yet the description enumerates the per-name result statuses and the extra fields returned for registered domains, and it explains the payment prerequisite. An agent has everything needed to call and interpret it.

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 parameter is self-documented, so the baseline of 3 is met. The description adds useful semantics the schema alone implies less clearly: the 10-name maximum applies per call and inputs are comma-separated domain names.

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 — bulk domain availability checks — and scopes it precisely (up to 10 names, registry RDAP with DNS fallback). This is clearly distinguishable from siblings like dns, rdap, ssl and subdomains, which each do one other thing.

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?

Opens with an explicit trigger — 'Use when naming a product, company or project and you need to know which domains are free' — so the calling context is unambiguous. It does not, however, name a sibling alternative (e.g. use rdap for a single-domain deep lookup), so routing between it and the other domain tools is left to inference.

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