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MailboxValidator Email Validation MCP Server

MailboxValidator Email Validation MCP Server

Official
by MailboxValidator
OverviewSchemaSourceRelated ServersDiscussions(1)Admin
TypeScript
Hybrid

validate_email

Check if an email address is valid and reachable to prevent bounces and improve deliverability.

Instructions

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

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "emailAddress": "<emailAddress>"
    },
    "name": "validate_email"
  }
}

Input Schema

NameRequiredDescriptionDefault
emailAddressYesEmail address to validate.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

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.

Deploy Server

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