DNS Doctor — Claude Code plugin & DNS skill (DMARC, SPF, DKIM)

Diagnose and fix a domain's email authentication (SPF, DMARC, DKIM, MX, blacklist, domain/SSL expiry) from inside Claude. This plugin bundles the DNS Doctor skill (the scan → diagnose → fix workflow) and an MCP server config pointing at the hosted DNS Doctor tools.

The moat: every fix record you get back is generated and validated by a deterministic engine — RFC grammar plus the SPF 10-lookup counter — never an LLM guess. Your agent hands the human a record that already parses correctly, not a plausible-looking string that silently fails.

What's inside

claude-plugin/
├── .claude-plugin/plugin.json   # plugin manifest
├── .mcp.json                    # MCP server: https://dnsdoctor.dev/mcp (HTTP)
├── skills/dns-doctor/SKILL.md   # the scan → diagnose → fix workflow
├── src/                         # @dnsdoctor/mcp — the local stdio MCP server
├── tools.json                   # the 15 tool definitions (generated, never hand-edited)
├── instructions.txt             # the server's own `initialize` guidance (generated)
├── tests/                       # vitest suite for the stdio server
├── package.json  tsconfig.json  # npm package + build
├── LICENSE                      # Apache-2.0
└── README.md

Tools it adds

| Tool | Does | |---|---| | scan_domain | Fresh scan of a domain; full report. | | get_report | Persisted report (scans once if none exists). | | build_dmarc_upgrade | A validated DMARC enforcement record — p=reject only when the server-derived alignment gate passes. | | count_spf_lookups | The SPF DNS-lookup count against the RFC limit of 10. | | validate_dmarc_record | Parse and validate a DMARC record, tag by tag. | | generate_dmarc_record | Build a DMARC record from a policy + reporting address. | | check_dkim_selector | Look up one DKIM selector and check the key. | | parse_dmarc_report | Parse an aggregate (RUA) report file into rows. | | check_record | Read any DNS record type for a name. | | check_reverse_dns | PTR / forward-confirmed reverse DNS for an IP. | | audit_spf_includes | The SPF include/redirect tree — who can transitively send as the domain, with typed findings (broken include, confirmed-unregistered include, expiring registration, nested +all). Analysis only; no SPF fix record. | | build_parked_domain_records | The Null MX + v=spf1 -all + p=reject; np=reject hardening pack for a domain that sends no mail. The server re-checks DNS itself and refuses when it finds evidence of mail. | | start_monitoring_signup | A sign-up link to hand to the human who owns the domain. Sends no email and creates nothing — they open it, sign in on our page themselves (a social provider or an emailed link, whichever that deployment offers), and the domain is carried over to their dashboard already filled in; monitoring starts once they verify it with a TXT record. | | get_alerts | Token required. The account's monitoring alert log, newest first. Read-only — no acknowledge, no delete. Page down with before until next_before is null before advancing since. | | get_readiness | Token required. Whether one monitored domain's aggregate-report evidence justifies a stronger DMARC policy yet: ready, the blockers, and next_record (validated, or null while blocked — which is an answer, not a gap). |

The two monitoring reads are listed for everyone and callable with a token: they appear in the tool list on both transports, and without a valid token the call is refused with the page the account owner mints one on. Over the hosted HTTP transport the dnsdoctor://domains resource (your monitored domains) is likewise always listed and refused without a token; the local stdio server registers the tools only — no resource. Anonymous access covers all thirteen diagnosis tools, which is enough for a one-off diagnosis either way.

Install

Claude Code

Add the marketplace/repo and enable the plugin:

/plugin marketplace add dnsdoctor/claude-plugin
/plugin install dns-doctor

Public home: github.com/dnsdoctor/claude-plugin (org dnsdoctor, domain-verified). The plugin is developed in the DNS Doctor monorepo and published here as clean release snapshots.

Or point Claude Code at a local checkout of this directory during development. Once enabled, the skill auto-loads and the dns-doctor MCP server connects to https://dnsdoctor.dev/mcp.

claude.ai (MCP connector)

Add a custom connector with:

• URL: https://dnsdoctor.dev/mcp
• Transport: Streamable HTTP
• Auth: none (anonymous) — or a Bearer token (below)

Optional: API token for monitored domains

Anonymous access covers scanning and fixes. A per-account API token unlocks the account's own monitoring data: the get_alerts and get_readiness tools, and the dnsdoctor://domains resource (your continuously-monitored domains and their latest per-check statuses).

1. Sign in at https://dnsdoctor.dev → Settings → API tokens → create a token. The plaintext (dnsd_…) is shown once; copy it.

2. Add the Authorization header to the server in .mcp.json:

   {
     "mcpServers": {
       "dns-doctor": {
         "type": "http",
         "url": "https://dnsdoctor.dev/mcp",
         "headers": { "Authorization": "Bearer ${DNSDOCTOR_API_TOKEN}" }
       }
     }
   }

   Then export DNSDOCTOR_API_TOKEN=dnsd_YOUR_TOKEN in your environment. Never commit the token.

Transport

Two supported public transports, same 15 tools:

• Hosted streamable HTTP — https://dnsdoctor.dev/mcp, wired in this plugin's .mcp.json. No install, no keys.
• Local stdio — npx -y @dnsdoctor/mcp. A thin server that runs on your machine and calls the public DNS Doctor REST API; it holds no diagnosis logic of its own and relays every record string verbatim.

{
  "mcpServers": {
    "dns-doctor": {
      "command": "npx",
      "args": ["-y", "@dnsdoctor/mcp"],
      "env": { "DNSDOCTOR_API_TOKEN": "dnsd_YOUR_TOKEN" }
    }
  }
}

DNSDOCTOR_API_TOKEN is optional (anonymous access covers scanning and fixes; the two monitoring reads need it). DNSDOCTOR_API_BASE overrides the origin — it must be an origin that serves the /api/… paths, i.e. the public site rather than a bare backend port.

Build the stdio server from source

npm ci
npm test
npm run build      # -> dist/index.js, the package's bin entrypoint

tools.json and instructions.txt are generated from the hosted server and pinned by a backend test — never hand-edit them, and never add a tool description to src/. Both files ship in the npm tarball; without them the client has no tools and none of its safety guidance.

Worked example

You: Our invoices keep landing in customers' spam. Domain is example.com.

Claude (scan_domain → example.com): DMARC is at p=none, so nothing enforces alignment — receivers can't tell your mail from a spoof. SPF passes with 7 of 10 lookups used. DKIM: a selector was found and is valid. Not blacklisted. Domain expires in 240 days.

Claude (build_dmarc_upgrade → example.com): SPF is aligned and DKIM is present, so enforcement to p=reject is safe. Publish this exact TXT record at _dmarc.example.com — paste it verbatim, don't edit it:

v=DMARC1; p=reject; rua=mailto:[email protected]; adkim=r; aspf=r

Apply it in your DNS host once you've confirmed it's approved, then ask me to re-scan to verify. Want the domain watched continuously with aggregate-report alerts? I can send a setup link to your email.

Learn more

• Methodology (how the verdicts are computed): https://dnsdoctor.dev/methodology
• REST API / OpenAPI schema: https://dnsdoctor.dev/api/v1/openapi.json

License

Apache-2.0 — see LICENSE.