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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuine behavioral context beyond them: the DNS/MX scope caps, the warning that resolution is not proof of registration or abuse, and the x402 payment model ($0.002 USDC, failed calls uncharged). The only blemish is the stated 'up to 30' DNS cap, which conflicts with the schema's 1-40 limit.

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?

Dense but well front-loaded: capability first, caveat second, pricing last. The technique enumeration and scope caps are informative, though the parenthetical dnstwist attribution is slightly decorative.

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?

An output schema exists, so return values need not be explained, and the description covers scope, the key interpretation caveat, and the payment model. The limit-count mismatch (30 vs 40) is the one gap an agent could trip on.

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 100%, so the schema already documents both parameters and the baseline is 3. The description restates the DNS lookup scope but introduces a '30' figure that clashes with the schema's 1-40 range, so it adds ambiguity rather than clarity.

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 (generates lookalike domains) plus the enumeration of techniques, the DNS A-record check, and the MX read. An agent can distinguish it from siblings like dns, domain, and subdomains without opening the 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?

The tool's use case (typosquat / brand-abuse reconnaissance) is implied by the technique list and caveat, but it never says when to pick this over dns or domain, nor any when-not condition. Usage is inferable rather than stated.

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