MailFixture

create_inbox

Create a programmatic email inbox and get its address. Call this at the start of a test flow, then drive the app under test with the returned email_address. Use one inbox per test for isolation.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "create_inbox"
  }
}

Input Schema

Name	Required	Description
`domain`	No	Domain the inbox lives on (fqdn). Omit for the shared utility domain; set to one of the account's verified custom domains otherwise.
`local_part`	No	Local part of the address (1-64 chars of [a-z0-9._-]). Omit for a random one — the safe default for inbox-per-test isolation.
`ttl_seconds`	No	Auto-delete after this many seconds (60..=2592000). Omit for no TTL. Prefer a TTL in test suites so abandoned inboxes clean themselves up.

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 11, 2026

TDQS

A4/5.0

Behavior3/5

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

No annotations provided, so description carries full burden. It describes creation and address retrieval but does not mention mutability, consequences, authorization, or cleanup behavior. Adequate but not exhaustive.

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?

Three concise, well-structured sentences with key information front-loaded. No wasted words.

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 creation tool with optional parameters and no output schema, the description is complete enough. Includes usage pattern and isolation advice. Minor gap: no mention of TTL or domain defaults.

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 has 100% description coverage, so baseline 3. Description adds no parameter-specific guidance beyond what schema 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?

Description clearly states the tool creates a programmatic email inbox and returns its address. The verb 'create' and resource 'inbox' are specific, and it distinguishes from siblings like clear_inbox or delete_inbox.

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?

Provides explicit advice: call at the start of a test flow, drive app under test with returned address, use one per test for isolation. Does not explicitly state when not to use, but context is clear.

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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