ProtonMail MCP Server

get_attachment

Read-only

Download a specific email attachment by providing the email ID and filename; use the optional index when filenames repeat.

Instructions

Download a specific attachment from an email

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": {
      "emailId": "<emailId>",
      "filename": "<filename>"
    },
    "name": "get_attachment"
  }
}

Input Schema

Name	Required	Description
`index`	No	0-based attachment index from get_email_by_id; required when filename is duplicated
`emailId`	Yes	Email ID (format: folder:uid)
`filename`	Yes	Attachment filename to retrieve

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv2.2.0Oct 5, 2026

addedInput schema / properties / index

Added value: +{
+  "description": "0-based attachment index from get_email_by_id; required when filename is duplicated",
+  "minimum": 0,
+  "type": "integer"
+}

First observedv2.0.0May 29, 2026

TDQS

C2.9/5.0

Behavior2/5

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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond the purpose restatement: it does not say how the attachment is delivered (inline content, base64, saved path) or whether authorization/scoping applies.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single efficient sentence with the resource and action front-loaded and zero filler. It is arguably too terse for a tool with no output schema, but there is no wasted text.

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?

With no output schema and no annotations covering return behavior, the description should explain what 'Download' yields — file content, a URL, or a local save. That gap matters for an agent that must handle the result, and it is left entirely unaddressed.

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 emailId format (folder:uid), filename, and the conditional index parameter are all documented in the schema. The description contributes no additional parameter meaning, which is the expected baseline when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Download) and resource (attachment from an email), which is distinguishable from get_email_by_id and get_emails at a glance. It does not explicitly name or contrast with any sibling, but the purpose is unambiguous.

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

Usage Guidelines2/5

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

No guidance on when to use this versus get_email_by_id or the other retrieval tools, and no mention of prerequisites. The condition for supplying 'index' (duplicated filenames) exists only in the schema, not the description.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server