Qualisend Email Verification

Explain a mail-server error code

lookup_smtp_code

Read-only

Explain a mail-server reply/error code (like 550 or 5.1.1) in plain English, and say whether it's a temporary hiccup or a permanent failure. No credit used. Available on the Qualisend Pro plan.

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": {
      "code": "<code>"
    },
    "name": "lookup_smtp_code"
  }
}

Input Schema

Name	Required	Description	Default
`code`	Yes	The SMTP code, e.g. 550 or 5.1.1.

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 14, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds valuable behavioral details: it states that no credit is used and that the tool is available on the Pro plan. It also clarifies the output behavior (whether the code is temporary or permanent), which goes beyond the annotation-only baseline.

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 two concise sentences, front-loaded with the main purpose and output. The second sentence adds cost and plan context without redundancy. Every word earns its place, and there is no fluff.

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?

For a simple single-parameter lookup tool with rich annotations and no output schema, the description is fully complete. It explains what the tool does, what the output will be (plain English and classification), cost implications, and availability. It also implicitly differentiates from all sibling tools. No coverage gaps remain.

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 already describes the 'code' parameter with examples. The description repeats these examples ('550 or 5.1.1') but does not add new semantic information beyond the schema. Thus it meets the baseline for high coverage without compensating gaps.

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 verb 'Explain' and the resource 'mail-server reply/error code', and specifies the output: plain English explanation and a temporary/permanent classification. It also distinguishes itself from sibling tools by focusing on code lookup rather than verification or DNS checks.

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 clear context—use this when you need to understand an SMTP error code—and mentions the Pro plan requirement, which helps an agent decide if the tool is available. It does not explicitly exclude alternative tools, but the sibling tools are clearly different in purpose, so the usage scenario is well implied.

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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