Mailcannon

send_test_email

Send a test email to yourself to preview formatting

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": {
      "subject": "<subject>",
      "body": "<body>"
    },
    "name": "send_test_email"
  }
}

Input Schema

Name	Required	Description
`body`	Yes
`subject`	Yes
`providerId`	No	Provider ID (optional, uses first available)

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 25, 2026

TDQS

B3.3/5.0

Behavior2/5

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

With no annotations, the description carries the full burden of behavioral disclosure. It only states the high-level action and does not reveal side effects (e.g., actual email delivery), authentication needs, or whether the email is queued or sent immediately. This leaves the agent unaware of potential consequences.

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 with no redundancy. It is front-loaded with the verb and efficiently conveys the tool's purpose.

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?

For a side-effectful tool that sends an email, the description is under-specified. It does not mention return values, success/failure handling, or configuration needs like an active provider. With no output schema and no annotations, more context is necessary for an agent to use it safely.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 33% (only providerId has a description). The tool description does not add meaning for the required subject and body parameters, and the optional providerId is explained only in the schema. The description adds minimal value beyond the schema.

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 action ('Send'), the target ('a test email to yourself'), and the purpose ('preview formatting'). This distinguishes it from sibling tools like check_email_spam_score or add_provider, which have different objectives.

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 phrase 'to preview formatting' implies the tool is for reviewing email appearance, but it does not explicitly say when to use this tool versus alternatives or mention any prerequisites like a configured provider. No exclusions or alternative tool mentions are provided.

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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