YourAITools MCP Hub

DomainCheck: Check a domain

check_domain

Read-onlyIdempotent

Check a domain before your agent trusts a link, a sender or a counterparty: does it exist, where does its mail go, SPF and DMARC policy, nameservers, DNSSEC. Free tier (preview). For registration age, registrar, parking detection and a 0-100 risk score use the paid x402 endpoint /v1/domain.

[DomainCheck via YourAITools MCP Hub] Free tier: same as DomainCheck's own MCP server (call without payment and without tier). Paid: domain $0.002 per call, with a credits key (Authorization: Bearer yatc_...) or x402 (USDC; the hub returns the payment terms). Failed tool calls aren't charged: credits are refunded automatically and x402 payments only settle on success.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "domain": "<domain>"
    },
    "name": "check_domain"
  }
}

Input Schema

Name	Required	Description	Default
`tier`	No	Paid tier: domain $0.002. Omit tier (with no credits key or x402 payment) to use the free tier.
`domain`	Yes	Domain, URL or email address

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 30, 2026
- addedInput schema / properties / domain / examples
```
Added value: +[
+  "example.com"
+]
```
First observedOct 24, 2026

TDQS

A4.5/5.0

Behavior5/5

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

The annotations already establish read-only, idempotent, open-world, non-destructive behavior. The description adds substantial operational context beyond annotations: free-tier preview behavior, paid pricing, credits-key versus x402 payment, and automatic refunds for failed calls.

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?

The purpose and checked attributes are front-loaded in the first sentence, which is effective. The second hub/payment paragraph is relevant but somewhat boilerplate and repetitive around free-versus-paid tier behavior.

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?

There is no output schema, but the description lists the checked aspects an agent can expect and fully covers billing/auth behavior. It does not describe the response shape or explicitly clarify sibling alternatives, so it is strong but not complete for a no-output-schema tool.

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 100%, so the domain and tier parameters are already documented structurally. The description still adds useful semantic context by explaining that omitting tier with no payment uses the free tier, and by describing the paid payment paths and pricing.

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?

The description gives a specific verb and resource — 'Check a domain' — and enumerates exactly what it checks: existence, mail routing, SPF/DMARC, nameservers, and DNSSEC. It also separates the free shallow check from the paid deeper endpoint for registration age, registrar, parking detection, and risk score, so the tool’s scope is clear 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.

Usage Guidelines4/5

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

It states a clear use context — before trusting a link, sender, or counterparty — and points to the paid x402 endpoint for additional domain data. It does not explicitly route agents away from overlapping siblings such as check_email or check_counterparty, so the alternative guidance is strong but not fully exhaustive.

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

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