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MailboxValidator

MailboxValidator Email Validation MCP Server

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by MailboxValidator
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TypeScript
Hybrid

MailboxValidator MCP server

This is a simple Model Context Protocol (MCP) server implementation for MailboxValidator API. It will return validation result for an email address.

mcp-mailboxvalidator MCP server

Features

  • Comprehensive Email Validation: Checking an email address to see if an email is reachable by checking the syntax, DNS, MX server, high risk, suppressed list, and more.

  • Disposable Email: Checking an email address to see if it's from a temporary/disposable email provider.

  • Free Email: Checking an email address to see if it's from a free email provider.

Requirement

This MCP server requires an API key. You can also sign up for a free API key and enjoy up to 300 queries per month.

The setup also uses Node.js and npm, which can be downloaded at Node.js website.

Setup

Follow the steps to use this MCP server with Claude Desktop:

  1. Download the repository to your local.

  2. Run the following commands while inside the project folder to install dependencies and build the server.

npm install
npm run build

  1. Make sure you have installed Claude Desktop. If you haven't, kindly download from here for Windows and macOS users, or follow this guide for Linux users.

  2. Open claude_desktop_config.json. If you don't have that file yet, follow this guide to create one.

  3. Add the following to your claude_desktop_config.json:

{
  "mcpServers": {
    "mailboxvalidator": {
      "command": "node",
      "args": [
        "C:\\path\\to\\mcp-mailboxvalidator\\build\\index.js"
      ],
      "env": {
        "MAILBOXVALIDATOR_API_KEY": "<YOUR_API_KEY>"
      }
    }
  }
}

  1. Remember to replace the path for the index.js with your actual path to your MailboxValidator MCP server on your local machine.

  2. To get your API key, just login to your dashboard and get it from there. Replace the <YOUR_API_KEY> in the above with your actual API key.

  3. Restart the Claude Desktop after saving the changes, and you should see it appear in the Search and tools menu.

Usage

Just enter your query about the email address in a chat in Claude Desktop. Some of example queries are:

  • Is (email) a valid email address?

  • Is (email) a fake email?

  • Is (email) a free email?

In Claude Desktop, the model will automatically generate the output based on the result returned by MailboxValidator MCP server.

Environment Variable

MAILBOXVALIDATOR_API_KEY

The free MailboxValidator API key allows you to query up to 300 emails per month. If you require more, you can sign up for a paid API plan.

Tool

validate_email

Description Validates the email address given. It helps users to determine if an email address is potentially reachable by checking the syntax, DNS, MX server, disposable list and more.

Arguments email (str): The email address to validate.

Returns A JSON string containing the validation data. The result includes the following fields:

  • Syntax: Checks that the email address conforms to how an email address should look like.

  • DNS & MX Server: Checks that the domain DNS has an MX server specified.

  • Network & Connectivity: Attempts connection to the MX server to make sure it's operational.

  • Greylisting: Checks if MX server is using greylisting that could cause email sent to that address to bounce.

  • Disposable List: Checks if the email domain is from a temporary or disposable email provider.

  • High Risk & Suppressed List: Checks if email username looks high-risk or if the email address is found in a suppression list.

  • Others: Checks the reputation score for the email and more..

If the request fails, the tool will return an error message as a string.

check_disposable_email

Description Checks if the email address given is from a disposable email provider.

Arguments email (str): The email address to check.

Returns A JSON string containing the disposable email data. The result includes the following fields:

  • Disposable List: Checks if the email domain is from a temporary or disposable email provider.

If the request fails, the tool will return an error message as a string.

check_free_email

Description Checks if the email address given is from a free email provider.

Arguments email (str): The email address to check.

Returns A JSON string containing the free email data. The result includes the following fields:

  • Free Email List: Checks if the email domain is from a free email provider.

If the request fails, the tool will return an error message as a string.

License

See the LICENSE file.

Available Tools

3 tools
check_disposable_emailB

Checks if an email address is a disposable email using MailboxValidator.

ParametersJSON Schema
NameRequiredDescriptionDefault
emailAddressYesEmail address to check.

TDQS

B3.1/5.0
Behavior2/5

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

No annotations; description only mentions the service used. Does not disclose any behavioral traits such as rate limits, authentication needs, or error handling.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Single sentence, no fluff, front-loaded with core information.

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

Completeness3/5

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

Low complexity tool with one parameter and no output schema. Description is adequate for basic understanding but lacks usage guidelines and behavioral details.

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 covers 100% of parameters with description. Tool description adds no extra meaning beyond the schema for the single parameter.

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?

Description clearly states it checks disposable email using MailboxValidator. Name and description differentiate from siblings check_free_email and validate_email, but no explicit contrast.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus siblings or alternatives. No context or exclusions provided.

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

check_free_emailB

Checks if an email address is a free email using MailboxValidator.

ParametersJSON Schema
NameRequiredDescriptionDefault
emailAddressYesEmail address to check.

TDQS

B3.1/5.0
Behavior2/5

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

No annotations provided; description only says 'checks' without disclosing if it's a read-only API call, potential side effects, or response details.

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?

Single sentence, front-loaded with the action, no fluff. However, it could be slightly more informative without losing conciseness.

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

Completeness2/5

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

No output schema, but description fails to explain the return value or what 'free email' means, leaving an agent without full context.

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 covers 100% of the single parameter with a description, so baseline is 3; description adds no extra meaning beyond what schema already provides.

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?

The description clearly states the tool checks if an email address is a free email using MailboxValidator, which distinguishes it from siblings like check_disposable_email and validate_email.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus siblings (check_disposable_email, validate_email) or context about prerequisites.

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

validate_emailA

Checks if an email address is valid and reachable using MailboxValidator.

ParametersJSON Schema
NameRequiredDescriptionDefault
emailAddressYesEmail address to validate.

TDQS

A3.8/5.0
Behavior3/5

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

No annotations are provided, so the description carries full burden. It mentions the use of MailboxValidator but does not disclose behavioral details such as API costs, rate limits, or what 'reachable' entails. Basic transparency is achieved but not enriched.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single concise sentence that conveys the essential functionality without any extraneous words. It is front-loaded and efficient.

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?

For a simple tool with one parameter and no output schema, the description provides sufficient context about its purpose and service. However, it could be more complete by hinting at the response format or what 'reachable' means.

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 coverage is 100% and the schema description for emailAddress is adequate. The tool description adds context about the validation service but does not add meaning beyond what the schema provides, so baseline score of 3 is appropriate.

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?

The description clearly states the tool checks if an email address is valid and reachable using MailboxValidator. It uses a specific verb and resource, and the mention of 'valid and reachable' distinguishes it from sibling tools that check for disposable or free emails.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for general email validation but does not explicitly state when to use this tool versus siblings like check_disposable_email or check_free_email. No guidance on prerequisites or exclusions is provided.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. 3 tool updatesv1.0.0
    • First observedcheck_disposable_email
    • First observedcheck_free_email
    • First observedvalidate_email
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TDQS

A3.7/5.0
Disambiguation5/5

Each tool targets a distinct aspect of email validation: disposable, free, and general validity/reachability. There is no overlap in their purposes.

Naming Consistency5/5

All tool names follow a consistent verb_noun pattern (check_disposable_email, check_free_email, validate_email) with snake_case, making them predictable.

Tool Count5/5

Three tools is a reasonable and focused set for an email validation server, covering key functions without unnecessary bloat.

Completeness4/5

The set covers primary email validation needs (disposable, free, general validity). Minor gaps like syntax-only checks are absent, but the core surface is solid.

Maintenance

ActivityInactive
ResponsivenessSyncing

Resources

Unclaimed servers have limited discoverability.

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