YourAITools MCP Hub

DomainCheck: Check an email address

check_email

Read-onlyIdempotent

Check an email address an agent is about to store, email or trust: syntax, disposable / throwaway provider, role account, free webmail. Free tier (no network). For MX, mail auth, domain age and a verdict (valid | risky | undeliverable) use the paid x402 endpoint /v1/email.

[DomainCheck via YourAITools MCP Hub] Free tier: same as DomainCheck's own MCP server (call without payment and without tier). Paid: email $0.001 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": {
      "email": "<email>"
    },
    "name": "check_email"
  }
}

Input Schema

Name	Required	Description	Default
`tier`	No	Paid tier: email $0.001. Omit tier (with no credits key or x402 payment) to use the free tier.
`email`	Yes	Email address

Schema Changelog

Changes observed during successful MCP inspections.

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

TDQS

A4.5/5.0

Behavior4/5

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

Adds real context beyond the annotations: the free tier performs no network calls, the paid tier costs $0.001 per call, auth is via Bearer credits key or x402, and failed calls are refunded / only settle on success. These are exactly the operational facts annotations don't cover. Minor gap: it never says what the free-tier response actually contains (fields, risk labels), so return behavior is only implied.

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 first paragraph front-loads the capability and the sibling hand-off in two tight sentences. The bracketed hub/pricing paragraph is denser and more boilerplate-like, but each sentence still carries payment or refund information an agent needs before calling. Slightly long overall but nothing is pure filler.

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?

With no output schema, the description should convey what comes back; it names the four checks performed and the verdict vocabulary of the paid endpoint, which is enough to set expectations. It stops short of describing the free-tier result structure or any error/refund signal shape, which is the remaining 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 100%, so the baseline is 3; the description earns a bump by explaining the meaning of the 'tier' enum value in terms of routing and price ('paid tier: email $0.001', omit to stay free) and by tying the paid path to specific extra checks. It does not add format hints for 'email' itself, which the schema already labels.

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 and resource ('Check an email address') and enumerates exactly what is evaluated: syntax, disposable/throwaway provider, role account, free webmail. It also explicitly contrasts itself with the paid /v1/email endpoint that adds MX, mail auth, domain age and a verdict, so an agent can separate it from siblings like check_domain or check_agent.

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

Usage Guidelines5/5

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

Gives a concrete trigger ('an email address an agent is about to store, email or trust') plus explicit routing guidance: free tier for syntax/reputation signals, paid endpoint for MX, mail auth, domain age and verdict. It also states the cost and how to invoke the paid path, leaving no ambiguity about which tool to pick.

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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