Clawhard Studio

Check a domain's email authentication (SPF, DKIM, DMARC, MX) from live DNS

stamp_check_email_domain

Read-onlyIdempotent

Use when the user asks why their email goes to spam, whether their domain is set up to send email, or before they launch a newsletter, cold outreach, transactional email or a new sending service, e.g. "why are my emails going to spam?", "is my SPF/DKIM/DMARC right?", "do I meet Gmail and Yahoo's sender requirements?" or "I added SendGrid, did I break SPF?". Reads public DNS (DNS-over-HTTPS) and checks: SPF (exactly one record, every include followed and DNS lookups counted per RFC 7208 against the limit of 10, void lookups, loops, +all/?all, ptr), DMARC (RFC 7489 syntax, policy, pct, alignment, inherited from the parent domain, and whether an external report address authorized it), DKIM (17 common selectors plus any you pass; key type and RSA key size read from the key, revoked or broken keys), and MX (provider, null MX). Returns a grade A-F, a verdict, each check with status pass/warn/fail/info, whether the Gmail, Yahoo and Outlook.com sender rules are met, and copy-ready DNS records to fix problems (e.g. one merged SPF record, a starter DMARC record). DNS cannot list DKIM selectors, so when none of the common selectors is found the result says so and a known selector (the s= value in a DKIM-Signature header) can be passed in. Accepts a domain, an email address or a URL. Results are cached for 5 minutes; pass fresh=true right after the user changes DNS.

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": "stamp_check_email_domain"
  }
}

Input Schema

Name	Required	Description
`fresh`	No	true to skip the 5-minute cache, e.g. right after a DNS change.
`domain`	Yes	The sending domain, e.g. mycompany.com. An email address (you@mycompany.com) or a URL also works.
`dkim_selectors`	No	Extra DKIM selectors to try besides the common ones, e.g. ["mxvault"]. Find it as s= in a DKIM-Signature header or in the provider's setup page.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 5, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already declare read-only, open-world, idempotent and non-destructive, so the bar is lower — yet the description still adds what actually matters: data source (public DNS-over-HTTPS), a 5-minute cache with a fresh bypass, the RFC 7208 lookup-limit and RFC 7489 evaluation rules applied, and the known limitation that DNS cannot enumerate DKIM selectors. It also discloses the shape of the result (grade A-F, verdict, per-check statuses, copy-ready fix records).

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 "Use when" trigger before the technical detail, which is the right ordering. It is a dense single block covering a lot of ground, so it is efficient rather than bloated, though the SPF/DMARC parentheticals could be trimmed.

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

Completeness5/5

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

Despite having no output schema, the description fully describes the return payload (grade, verdict, per-check status, sender-rule compliance, remediation records) and the one semantic limitation an agent must know about DKIM selector discovery. Nothing needed to call this correctly is missing.

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 3 is the baseline, but the description earns an extra point by explaining that domain accepts a bare domain, an email address or a URL, and by contextualizing dkim_selectors (17 common selectors tried first, plus any supplied as s= from a DKIM-Signature header). The fresh/cache explanation is partly redundant with the schema text.

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 — reads live DNS (DoH) and checks SPF, DKIM, DMARC and MX — and enumerates the exact checks performed. An agent can tell this apart from the generic sibling stamp_check_dns_record because the description scopes it to email authentication.

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 rich trigger context with user-style utterances ("why are my emails going to spam?", "I added SendGrid, did I break SPF?") and a proactive-use case (before launching a newsletter or cold outreach). It stops short of naming a when-not condition or pointing at an alternative tool, so it falls just shy of a 5.

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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