Quiet Failures

Check email authentication (live)

check_email_auth

Read-only

Live SPF, DKIM and DMARC audit of up to 50 domains the user owns or asks about. Returns a per-domain breakdown plus a portfolio grade. Compare against the base rates: most of the web fails these controls. Rate-limited per client.

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": {
      "domains": "<domains>"
    },
    "name": "check_email_auth"
  }
}

Input Schema

Name	Required	Description	Default
`domains`	Yes	Domains to audit (1-50). Array preferred; a JSON-encoded array or comma/space-separated string also works.

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 17, 2026

TDQS

A4.5/5.0

Behavior5/5

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

The description adds valuable behavioral context beyond the annotations (readOnlyHint, openWorldHint): 'live' indicates real-time execution, 'Rate-limited per client' discloses constraints, and 'most of the web fails these controls' sets performance expectations. No contradiction with annotations.

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 three sentences, front-loaded with the core action, and every sentence contributes unique information (action, returns, base-rate comparison, rate limit). No fluff or redundancy.

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

Completeness5/5

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

Despite lacking an output schema, the description clearly states the return type ('per-domain breakdown plus a portfolio grade') and notes rate limiting. This is sufficient for a straightforward audit tool, and the comparison to base rates adds decision-making 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 coverage is 100%, with the parameter description already detailing accepted formats and the 1-50 domain limit. The description's mention of 'up to 50 domains' and 'owns or asks about' adds authorization context but does not enhance parameter structure or syntax. Baseline 3 for high schema coverage 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 specific action ('Live SPF, DKIM and DMARC audit') and resource ('up to 50 domains'). It distinguishes itself from siblings like check_subdomain_takeover and check_whois by focusing on email authentication. The scope ('the user owns or asks about') adds precision.

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?

The description gives usage context by suggesting comparison to base rates and noting rate limits per client. However, it does not explicitly state when to use this tool over alternatives or provide exclusions. This is clear but lacks the explicit 'use X instead' guidance seen in top-tier examples.

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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