Domain Trust Check (DNS, Email Auth, TLS, Headers)

domain_check

Sanity-check a vendor's or sender's domain before trusting an email, link or payment request. Measured at request time: A/AAAA, NS and MX records, SPF and DMARC policies, DNSSEC (DS), CAA, the TLS certificate on port 443 (issuer, validity, hostname match) and HTTPS security headers, with a list of risk flags. Technical signals only, not a reputation or ownership verdict. Use when an unfamiliar domain appears in an invoice, email or supplier record. $0.003 per call, USDC on Base (x402).

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "domain_check"
  }
}

Input Schema

Name	Required	Description	Default
`domain`	No	Domain name, e.g. example.com (no scheme or path)
`payment_signature`	No	x402 v2 PAYMENT-SIGNATURE header value. Omit to receive payment requirements.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 16, 2026

TDQS

A4.5/5.0

Behavior5/5

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

With no annotations, the description carries the full burden and does so well: it discloses that checks happen at request time, that results are technical signals not a reputation/ownership verdict, that risk flags are returned, and that payment is $0.003 per call in USDC on Base via x402. Auth/payment prerequisites are surfaced rather than hidden.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the purpose and trigger before the long signal enumeration and pricing tail; every clause carries information. The middle signal list is dense but each item is substantive, so little is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with no annotations and no output schema, the description covers what is measured, the limits of the result (technical only, not a verdict), and the payment flow. It stops short of describing the returned risk-flag structure, which is the only material gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is already 100%, so the baseline is 3, but the description adds genuinely useful semantics beyond the schema: the x402 payment model, per-call cost, and the fact that payment_signature is what unlocks results rather than a plain argument.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('sanity-check') and resource ('vendor's or sender's domain') and then enumerates the exact record classes inspected (A/AAAA, NS, MX, SPF, DMARC, DNSSEC DS, CAA, TLS cert, security headers). No siblings exist, so the scope is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete trigger: 'Use when an unfamiliar domain appears in an invoice, email or supplier record.' No alternatives or when-not-to-use conditions are needed since there are no sibling tools, but no explicit exclusion is stated either.

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

All Domain Trust Check (DNS, Email Auth, TLS, Headers) tools Inspect

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