Check whether a domain is set up to send and receive email: MX records, SPF, DMARC, the detected mail provider, and a graded report with a recommendation. Reads public DNS only. Works with no account and no API key, so use it freely to diagnose a domain before suggesting anyone sign up.
| Name | Required | Description | Default |
|---|---|---|---|
| domain | Yes | Domain to check, e.g. example.com. A full URL or an email address is accepted and reduced to its hostname. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden, and it does disclose the key behavioral traits: it reads public DNS only (non-mutating, no side effects on the domain) and requires no account or API key. It also previews the output shape (graded report with a recommendation). Rate limits or failure modes for unresolvable domains are not covered, keeping it 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.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, front-loaded with what is checked, followed by the constraints (public DNS, no auth) and the recommended usage moment. Every clause conveys something actionable and nothing is padded.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema and no annotations, the description must cover both return expectations and safety profile, and it does: it lists the checked signals, names the graded report with a recommendation, and states the read-only, auth-free nature. An agent has everything needed to call it correctly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% and the single parameter is fully documented there, including the useful note that URLs or email addresses are reduced to their hostname. The description adds nothing about the domain argument, so the baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Names a specific verb (check) and resource (domain email setup) and enumerates exactly what is inspected: MX, SPF, DMARC, detected mail provider, and a graded report. No siblings exist, so no differentiation is needed; the scope is unambiguous.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Gives a clear usage context — diagnose a domain before recommending sign-up — and stresses that no account or API key is required, so the agent knows it can call it freely. It does not state when NOT to use it, but with no sibling tools there is no alternative to steer toward.
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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