proton-bridge-mcp

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List folders and labels

list_folders

Read-only

Retrieve Proton folder and label names over the Bridge so you can file and tag messages correctly; optionally inspect one folder’s counts and UIDVALIDITY before acting on stored UIDs.

Instructions

List all Proton folders and labels available over the Bridge. Call this first to learn exact folder/label names for filing and tagging. Pass folder to get that folder's message counts plus UIDNEXT and UIDVALIDITY instead: UIDs are only valid within one UIDVALIDITY generation, so check it before acting on uids noted earlier.

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": "list_folders"
  }
}

Input Schema

Name	Required	Description	Default
`folder`	No	Report this one folder's counts and UIDVALIDITY instead of listing every folder.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv2.0.0Oct 24, 2026

addedInput schema / properties / folder

Added value: +{
+  "description": "Report this one folder's counts and UIDVALIDITY instead of listing every folder.",
+  "type": "string"
+}

First observedv1.2.1Aug 11, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Annotations only say readOnlyHint/openWorldHint; the description adds substantive behavior: the folder mode returns counts plus UIDNEXT and UIDVALIDITY, and it warns that UIDs are only valid within a single UIDVALIDITY generation. That caveat is exactly the kind of operational context annotations cannot convey.

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?

Three tight sentences with the primary action and the 'call this first' rule front-loaded. The dense UID sentence is justified but slightly packed, keeping it short of a 5.

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, annotations covering safety, and only one optional parameter, the description covers when to call, the alternate mode, and the UID hazard. It leaves the shape of the returned folder/label list implicit, a minor gap for a discovery tool.

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

Parameters4/5

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

Schema coverage is 100%, so baseline is 3, but the description adds value beyond the schema by naming UIDNEXT (not mentioned in the schema) and framing the folder argument as a mode switch rather than a filter. The UIDVALIDITY caveat further clarifies why an agent would request that mode.

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 ('List all Proton folders and labels') and scopes it to the Bridge. It distinguishes itself from siblings like move_to_folder or apply_label by being the enumeration source those tools depend on.

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?

Explicitly says 'Call this first to learn exact folder/label names for filing and tagging,' which gives a clear ordering rule relative to filing/tagging siblings. It also explains the alternative mode (pass folder), though it doesn't name any sibling tool outright or state an exclusion.

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