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List Folders

mailbox_list_folders

Read-onlyIdempotent

List mailbox folders to review available destinations before filing or moving messages. Read-only operation returns folders with pagination support.

Instructions

Use this to inspect mailbox folders before filing or moving messages. It is read-only.

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Maximum results (default 50, max 100).
`cursor`	No	Pagination cursor — the `next_cursor` from the previous response.
`mailbox_id`	No	Mailbox public ID to target when the credential grants access to more than one mailbox. Omit when the credential is scoped to exactly one mailbox.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv1.0.8Sep 15, 2026

addedOutput schema / $schema

Added value: +"https://json-schema.org/draft/2020-12/schema"

removedOutput schema / additionalProperties
```
Removed value: -true
```

addedOutput schema / properties

Added value: +{
+  "result": {
+    "allOf": [
+      {
+        "properties": {
+          "meta": {
+            "additionalProperties": {},
+            "properties": {},
+            "type": "object"
+          },
+          "ok": {
+            "enum": [
+              true
+            ],
+            "type": "boolean"
+          }
+        },
+        "required": [
+          "ok",
+          "meta"
+        ],
+        "type": "object"
+      },
+      {
+        "properties": {
+          "data": {
+            "items": {
+              "additionalProperties": false,
+              "properties": {
+                "can_add_items": {
+                  "description": "Whether messages can be moved into this folder.",
+                  "type": "boolean"
+                },
+                "id": {
+                  "description": "Folder ID",
+                  "type": "string"
+                },
+                "name": {
+                  "type": "string"
+                },
+                "parent_id": {
+                  "type": [
+                    "string",
+                    "null"
+                  ]
+                },
+                "role": {
+                  "description": "System role when the folder is a built-in folder.",
+                  "type": [
+                    "string",
+                    "null"
+                  ]
+                },
+                "sort_order": {
+                  "type": [
+                    "integer",
+                    "null"
+                  ]
+                },
+                "total_messages": {
+                  "type": "integer"
+                },
+                "unread_messages": {
+                  "type": "integer"
+                }
+              },
+              "required": [
+                "id",
+                "name",
+                "parent_id",
+                "role",
+                "sort_order",
+                "total_messages",
+                "unread_messages",
+                "can_add_items"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "meta": {
+            "additionalProperties": false,
+            "properties": {
+              "request_id": {
+                "example": "req_clxxxxxxxxxxxxxxxxxxxxxxxxx",
+                "type": "string"
+              }
+            },
+            "required": [
+              "request_id"
+            ],
+            "type": "object"
+          },
+          "pagination": {
+            "additionalProperties": false,
+            "properties": {
+              "has_more": {
+                "type": "boolean"
+              },
+              "next_cursor": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "has_more"
+            ],
+            "type": "object"
+          }
+        },
+        "required": [
+          "data",
+          "pagination"
+        ],
+        "type": "object"
+      }
+    ],
+    "unevaluatedProperties": {
+      "not": {}
+    },
+    "x-fastmcp-top-level-schema": "MailboxFolderCursorListResponse"
+  }
+}

addedOutput schema / required
```
Added value: +[
+  "result"
+]
```

First observedv1.0.0Jul 13, 2026

TDQS

A3.9/5.0

Behavior3/5

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

Annotations already carry readOnlyHint, idempotentHint, and destructiveHint=false; the description merely restates 'read-only' and adds no new behavioral traits like pagination or auth. No contradiction.

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 short sentences, front-loaded with purpose and no filler. Every word earns its place.

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 full schema coverage, an output schema present, and annotations covering read-only and idempotent behavior, the description's purpose and use-case complete the picture.

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%, and the description relies on the schema for parameter details. It adds no extra semantics, which meets the baseline.

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?

Description identifies a specific verb ('inspect') and resource ('mailbox folders'), plus a clear use case. It doesn't explicitly differentiate from sibling tools, but 'folders' is distinct among the sibling list.

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?

States a concrete trigger: before filing or moving messages. It doesn't mention alternatives or when not to use, so it doesn't reach a 5.

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