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Apple Mail MCP

Apple Mail MCP

by cyberprive
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

list_attachments

Read-only

Lists attachments on a specified email message, returning each attachment’s index, name, size, MIME type, and download status so you can choose which one to save.

Instructions

List attachments on a message.

Args: account, mailbox, id: As returned by search_messages.

Returns a list of {index, name, size, mime_type, downloaded}. Pass index to save_attachment. downloaded=false means the attachment body isn't on disk yet — open the message in Mail.app to fetch it before saving.

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": {
      "account": "<account>",
      "mailbox": "<mailbox>",
      "id": "<id>"
    },
    "name": "list_attachments"
  }
}

Input Schema

NameRequiredDescriptionDefault
idYes
accountYes
mailboxYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.2.0

TDQS

A4.3/5.0
Behavior4/5

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

The readOnlyHint annotation already declares this is a safe read operation, and the description adds meaningful behavior: it lists the return fields and explains that downloaded=false means the attachment body is not yet on disk and must be fetched by opening the message in Mail.app. This is useful operational context beyond the annotations, though pagination and error behavior are not covered.

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 purpose is front-loaded in one sentence, followed by compact Args and Returns sections. Every sentence adds useful information: parameter origin, return fields, the save_attachment handoff, and the downloaded=false caveat.

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 read-only listing tool with no output schema, the description is complete enough: it states the resource, required inputs, return shape, downstream save workflow, and the key downloaded-flag caveat. Annotation coverage already establishes the read-only safety profile.

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 0%, so the description must compensate. It identifies all three parameters and explains that account, mailbox, and id are 'as returned by search_messages,' which adds origin context, but it does not describe expected formats or constraints for account or mailbox.

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 opens with a specific verb and resource: 'List attachments on a message.' It also distinguishes the tool from save_attachment by explaining that the returned index is passed to save_attachment, and it ties the required arguments to search_messages.

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 clearly connects this tool to the search-then-save workflow: arguments come from search_messages, and the returned index is passed to save_attachment. It does not explicitly name when not to use this tool or compare it against save_all_attachments, but the primary usage 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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