Unstuck

Domain, DNS, Email and SSL Lookup

domain_info

Read-onlyIdempotent

Look up everything about a domain: WHOIS-style registration data (registrar, creation and expiry dates via RDAP), DNS records (A, AAAA, MX, NS, TXT), email security (parsed SPF and DMARC), and the website's SSL/TLS certificate issuer and expiry date. Use it to research a company's domain, check when a domain or certificate expires, debug DNS or email deliverability, or verify who hosts a site. Price: $0.01 per successful call; failed calls are free. Free to try: a few calls a day without a key.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`domain`	Yes	The domain or hostname to inspect, e.g. "example.com".
`api_key`	No	Your Unstuck API key, if this connection has none. Leave empty to try free tools or to get a key and payment link.

Output Schema

TableJSON Schema

Name	Required	Description
`dns`	Yes
`spf`	Yes	Parsed SPF record, or null if none.
`tls`	Yes	Certificate on port 443, or an error.
`dmarc`	Yes	Parsed DMARC record, or null if none.
`domain`	Yes	The host that was inspected.
`balance_usd`	Yes	Remaining prepaid balance, USD.
`charged_usd`	Yes	Amount charged for this call, USD.
`registration`	Yes	RDAP registration data, or an error.
`registrable_domain`	Yes	The registrable domain (e.g. example.com).

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 4, 2026

addedInput schema / properties / api_key

Added value: +{
+  "description": "Your Unstuck API key, if this connection has none. Leave empty to try free tools or to get a key and payment link.",
+  "maxLength": 200,
+  "type": "string"
+}

First observedOct 4, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful non-obvious context the annotations cannot convey: $0.01 per successful call, failed calls free, and a free tier of a few calls per day without a key — a real cost/rate consideration for an agent deciding whether to call.

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 capability list is front-loaded in one dense sentence and the usage sentence follows immediately; the pricing sentence is arguably promotional but is short and decision-relevant. No wasted preamble or redundancy.

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 an output schema present, the description need not explain return structure, and it does summarize the data categories returned. Combined with the required domain parameter and the free-tier/pricing note, an agent has enough to call it correctly, though the missing differentiation from 'domain_check' leaves a small routing gap.

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 both parameters (domain, api_key) are already documented in the schema, including an example value for domain. The description adds no syntax, normalization, or format guidance beyond what the schema provides, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('look up') and resource (a domain) and enumerates exactly what is covered: RDAP/WHOIS registration data, DNS records, SPF/DMARC, and SSL certificate issuer/expiry. It does not, however, distinguish itself from the sibling 'domain_check', which sounds like an overlapping capability an agent could confuse it with.

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 gives four concrete usage contexts (research a company's domain, check domain/certificate expiry, debug DNS or email deliverability, verify who hosts a site), which is clear when-to-use guidance. It offers no when-not-to-use or explicit alternative routing, so it stops short 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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