EXZA Remote

Preview email message

exza_preview_email_message

Read-onlyIdempotent

Prepare a non-sending preview of an email. Unlike exza_create_email_draft it does not open macOS Mail; unlike exza_send_email_message it never sends a message. Requires account-bound computer:read OAuth.

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": {
      "to": "<to>",
      "subject": "<subject>",
      "body": "<body>"
    },
    "name": "exza_preview_email_message"
  }
}

Input Schema

Name	Required	Description
`to`	Yes	New destination path; overwrites are refused where described.
`body`	Yes	Email body; do not include secrets.
`subject`	Yes	Email subject; verify before sending.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 7, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is known; the description still adds value by guaranteeing no Mail app launch, no message transmission, and stating the required account-bound computer:read OAuth scope. It does not say what the preview result contains or how it is surfaced, which is the remaining gap.

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 short sentences, front-loaded with the core action, then the differentiators, then the auth prerequisite. No filler or restatement of the title.

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?

With no output schema, an agent still lacks information about what the preview returns (rendered text, structured headers, or just a confirmation), and the description is silent on that. Otherwise the safety, alternatives, and auth requirement are fully covered for a simple three-parameter read-only tool.

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 description coverage is 100%, so the three required parameters (to, subject, body) are already documented in structured fields. The description adds no format, validation, or semantic detail beyond what the schema provides, so the baseline 3 applies.

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?

States a specific verb and resource ('Prepare a non-sending preview of an email') and immediately distinguishes itself from the two nearest siblings, exza_create_email_draft and exza_send_email_message. An agent can identify the tool's role without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit exclusion guidance against both alternatives: it does not open macOS Mail (unlike the draft tool) and it never sends (unlike the send tool). This effectively defines the selection condition — preview without side effects — leaving nothing material to inference.

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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