stack-and-dns-mcp

Verify Email Infrastructure & Deliverability

verify_email_infrastructure

Read-onlyIdempotent

Run live DNS checks on a domain’s email setup to detect SPF, DKIM, DMARC, MX, MTA-STS and BIMI issues, returning severity-sorted spoofing and deliverability risks with fixes and a 0–100 score.

Instructions

Run live DNS checks on a domain's email setup: MX records with provider identification (Google Workspace, Microsoft 365, Proofpoint...), SPF parsing with recursive include resolution and the 10-lookup limit, DKIM key discovery across 86 common selectors (key type and length), DMARC policy and reporting configuration (with organizational-domain fallback), MTA-STS, TLS-RPT, BIMI and disposable-domain detection. Returns a severity-sorted list of deliverability and spoofing risks with remediation advice, the detected sending platforms, and a 0-100 deliverability score with a per-component breakdown. Use it before outbound campaigns, to validate lead domains, or to audit a prospect's email security. Cost: 1 credit.

Input Schema

Name	Required	Description
`domain`	Yes	Domain to inspect. Accepts a bare hostname ("example.com"), a URL ("https://www.example.com/pricing") or an email address ("jane@example.com"). Scheme, path, port and query are stripped; IDN names are accepted.
`checkMtaSts`	No	Fetch and validate the MTA-STS policy file over HTTPS when a _mta-sts record exists.
`dkimSelectors`	No	Extra DKIM selectors to probe, e.g. ["google", "selector1", "k1"]. 86 common provider selectors are always probed.

Output Schema

Name	Required	Description	Default
`mx`	Yes
`spf`	Yes
`bimi`	Yes
`dkim`	Yes
`dmarc`	Yes
`grade`	Yes
`risks`	Yes
`score`	Yes
`domain`	Yes
`exists`	Yes
`mtaSts`	Yes
`tlsRpt`	Yes
`billing`	Yes
`summary`	Yes
`timings`	Yes
`nxdomain`	Yes
`checkedAt`	Yes
`providers`	Yes
`disposable`	Yes
`riskCounts`	Yes
`inputDomain`	Yes
`isSubdomain`	Yes
`scoreBreakdown`	Yes
`organizationalDomain`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.1Nov 4, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior, and the description adds real context beyond that: live DNS lookups, recursive SPF include resolution capped at the 10-lookup limit, 86 selector probes, organizational-domain DMARC fallback, and a per-call cost of 1 credit. It does not discuss failure modes for unreachable domains or per-call latency, so it falls just short of a 5.

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?

A single front-loaded paragraph that leads with the action and check inventory before moving to outputs and intended use cases, so the agent gets the essentials first. The dense enumeration of record types and the return-value sentence run long, but each clause carries information rather than filler.

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?

Even though an output schema exists and return values need not be restated, the description covers scope, cost, scoring, and remediation output, which is everything an agent needs to decide and call correctly for a read-only multi-check DNS tool.

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

Parameters3/5

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

Schema description coverage is 100%, so all three parameters are already documented with formats, defaults and limits, making 3 the baseline. The description adds only marginal meaning (86 default selectors always probed) that slightly contextualizes dkimSelectors without redefining domain or checkMtaSts.

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?

Opens with a specific verb and resource ("Run live DNS checks on a domain's email setup") and then enumerates the exact record families inspected (MX, SPF, DKIM, DMARC, MTA-STS, TLS-RPT, BIMI), so the agent can distinguish it from siblings like inspect_tech_stack or comprehensive_audit at a glance.

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 three concrete triggering scenarios (before outbound campaigns, lead-domain validation, prospect security audit), which is strong when-to-use guidance. It stops short of explicit exclusions or naming which sibling to prefer for overlapping broad audits, so it is not a full when/when-not statement.

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

Deploy Server