outlook-local-mcp

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list_mailboxes

Read-only

Enumerate mailbox stores already accessible in the running Outlook profile, including archives and shared stores, without adding accounts or requesting access.

Instructions

List mailbox stores already accessible through the running Outlook profile. Includes mounted archives and shared stores; does not add accounts or request access.

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_mailboxes"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`items`	Yes
`omitted`	No
`warnings`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.2.1Sep 12, 2026

addedOutput schema / $defs / Mailbox / properties / sending_accounts

Added value: +{
+  "items": {
+    "$ref": "#/$defs/Person"
+  },
+  "title": "Sending Accounts",
+  "type": "array"
+}

addedOutput schema / $defs / Person

Added value: +{
+  "properties": {
+    "email": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "title": "Email"
+    },
+    "name": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "title": "Name"
+    }
+  },
+  "required": [
+    "name",
+    "email"
+  ],
+  "title": "Person",
+  "type": "object"
+}

First observedv0.1.0Sep 11, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuine context beyond that: it enumerates what is returned (mounted archives, shared stores) and explicitly disclaims account creation or access requests, which an agent needs in order to set expectations.

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?

Two compact sentences with the primary action front-loaded and the inclusion/exclusion caveat immediately after. No filler.

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?

With no parameters, an output schema present, and annotations covering the safety profile, the description supplies everything else an agent needs: what is enumerated and what the call will not do.

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?

The tool takes zero parameters, so there is nothing for the description to clarify; per the baseline for parameterless tools this is a 4. The description correctly implies the call is unconditional.

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 (List) and resource (mailbox stores) and scopes it to 'already accessible through the running Outlook profile', which separates it from sibling tools like list_folders. It does not name a sibling explicitly, but the resource is distinct enough for disambiguation.

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

Usage Guidelines3/5

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

The clause 'does not add accounts or request access' sets a useful negative boundary, steering the agent away from expecting provisioning behavior. However, there is no explicit statement of when to call this versus list_folders or outlook_status, so usage is only implied.

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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