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Batch Update Messages

mailbox_batch_update_messages

Idempotent

Update multiple email messages at once: set seen or flagged status, move to folders, or apply keywords after user confirms the change. Not for read-only tasks.

Instructions

Use this to mark, flag, move to a folder, or set keywords/labels on multiple messages after the user has confirmed the desired change. Do not use it for read-only tasks.

Input Schema

TableJSON Schema

Name	Required	Description
`ids`	No	Message IDs to update, maximum 100.
`seen`	No	Set or clear the seen flag.
`flagged`	No	Set or clear the flagged marker.
`keywords`	No	Map of message keyword names to booleans. `true` sets the keyword; `false` clears it. Keyword names are normalised to lowercase. Lifecycle keywords such as `$draft` are read-only.
`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.
`if_in_state`	No	Optional message state token for stale-write protection.

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": {
+            "additionalProperties": false,
+            "properties": {
+              "failed": {
+                "items": {
+                  "additionalProperties": false,
+                  "properties": {
+                    "code": {
+                      "type": "string"
+                    },
+                    "id": {
+                      "type": "string"
+                    },
+                    "message": {
+                      "type": "string"
+                    }
+                  },
+                  "required": [
+                    "id",
+                    "code",
+                    "message"
+                  ],
+                  "type": "object"
+                },
+                "type": "array"
+              },
+              "not_found": {
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              },
+              "states": {
+                "additionalProperties": false,
+                "properties": {
+                  "new_state": {
+                    "type": [
+                      "string",
+                      "null"
+                    ]
+                  },
+                  "old_state": {
+                    "type": [
+                      "string",
+                      "null"
+                    ]
+                  }
+                },
+                "required": [
+                  "old_state",
+                  "new_state"
+                ],
+                "type": "object"
+              },
+              "updated": {
+                "items": {
+                  "type": "string"
+                },
+                "type": "array"
+              }
+            },
+            "required": [
+              "updated",
+              "not_found",
+              "failed",
+              "states"
+            ],
+            "type": "object"
+          },
+          "meta": {
+            "additionalProperties": false,
+            "properties": {
+              "request_id": {
+                "example": "req_clxxxxxxxxxxxxxxxxxxxxxxxxx",
+                "type": "string"
+              }
+            },
+            "required": [
+              "request_id"
+            ],
+            "type": "object"
+          }
+        },
+        "required": [
+          "data"
+        ],
+        "type": "object"
+      }
+    ],
+    "unevaluatedProperties": {
+      "not": {}
+    },
+    "x-fastmcp-top-level-schema": "MailboxBatchUpdateMessagesResultResponse"
+  }
+}

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

First observedv1.0.0Jul 13, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already cover readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the description's job is to add context beyond those. It adds a meaningful workflow constraint (invoke only post user-confirmation) and reinforces the mutating nature of the call, consistent with the annotations. No contradiction exists, and the added context is genuinely useful for an agent deciding whether to act autonomously.

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 sentences with zero filler: the operations list is front-loaded, the user-confirmation gate follows immediately, and the read-only exclusion closes it out. Every sentence carries load-bearing guidance for invocation.

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 an output schema present and annotations covering idempotency and destructiveness, the description need not explain return values or safety profiles. It covers purpose, when-to-use, and exclusions adequately. The residual gap is the unsupported 'move to a folder' claim and no guidance that ids is semantically required despite the empty required array, leaving minor ambiguity for the agent.

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 schema already documents all six parameters, including rich detail on keywords (normalization to lowercase, read-only lifecycle keywords) and if_in_state (stale-write protection). The description adds only loose alignment ('set keywords/labels' maps to the keywords param) and no syntax or format details beyond the schema. Baseline 3 applies.

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?

The description names a specific resource (multiple messages) and concrete operations (mark, flag, set keywords/labels), which distinguishes it from sibling update-adjacent tools like mailbox_batch_delete_messages and mailbox_batch_get_messages. However, the claimed 'move to a folder' capability has no corresponding parameter in the input schema, which slightly muddies the purpose for an agent planning its call.

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 gives an explicit when-to-use condition ('after the user has confirmed the desired change') and a clear when-not-to-use exclusion ('Do not use it for read-only tasks'). It stops short of naming the specific read-only siblings (e.g., mailbox_batch_get_messages, mailbox_get_message) as alternatives, which would earn a 5.

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