Previous value: -"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both."New value: +"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both — a pair naming different mailboxes is refused."

Previous value: -"Which operation to perform. Determines which other arguments are used."New value: +"Operation to run. create = queue to, subject and body for send_at; cancel = a pending send by `id`."

Previous value: -[
-  "create",
-  "list",
-  "cancel"
-]New value: +[
+  "create",
+  "cancel"
+]

Previous value: -"Optional file attachments. Maximum 20 items. Total size must not exceed 10 MB."New value: +"File attachments, 10 MB total. Inline base64 only here — the { source_message_id, attachment_index } reference form is email_compose's, not this tool's."

Previous value: -"Base64-encoded attachment content."New value: +"Base64-encoded content."

Previous value: -"Attachment filename."New value: +"Filename the recipient sees."

Previous value: -"MIME type of the attachment."New value: +"MIME type."

Previous value: -"List of BCC recipient email addresses. Optional."New value: +"Bcc addresses."

Previous value: -"Email body as plain text. If html_body is also provided, the message is sent as multipart/alternative."New value: +"Plain-text body. Sent as multipart/alternative when html_body is given too."

Previous value: -"List of CC recipient email addresses. Optional."New value: +"Cc addresses."

Previous value: -"Optional HTML version of the email body."New value: +"Optional HTML body."

Previous value: -"UUID of the scheduled send to cancel, as returned by schedule_create and schedule_list. Alias of scheduled_send_id."New value: +"Scheduled send UUID from a create or list call."

Added value: +{
+  "description": "Reuse only when retrying the identical request within 24 hours; the retry is collapsed, not repeated. Reuse with different arguments is rejected.",
+  "maxLength": 200,
+  "minLength": 1,
+  "type": "string"
+}

Previous value: -"Email address of the inbox to use, as a friendly alternative to inbox_id. Optional; ignored if inbox_id is given."New value: +"Inbox email address, an alternative to inbox_id."

Previous value: -"UUID of the inbox to use. Optional when the API key has access to exactly one inbox (it is auto-selected). Alternatively pass `inbox` with an email address. If you don't know the inbox_id and several are accessible, just omit it — the response then lists every inbox with its inbox_id so you can retry (calling inbox_list does the same)."New value: +"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both."

Removed value: -{
-  "default": 20,
-  "description": "Maximum number of results to return. Defaults to 20.",
-  "maximum": 100,
-  "minimum": 1,
-  "type": "integer"
-}

Previous value: -"Optional Reply-To header address."New value: +"Reply-To address."

Removed value: -{
-  "description": "UUID of the scheduled send to cancel. Alias of `id` — provide either field.",
-  "format": "uuid",
-  "type": "string"
-}

Previous value: -"ISO 8601 datetime string (with timezone) at which the message should be sent. Must be in the future. Example: '2026-06-01T09:00:00Z' or '2026-06-01T09:00:00+02:00'. The dispatcher runs every minute so the actual send time may be up to 60 seconds after send_at."New value: +"Send time, in the future and carrying a timezone (e.g. '2026-06-01T09:00:00+02:00'). The dispatcher runs every minute, so delivery can be up to 60s late."

Previous value: -"Email subject line. Must be non-empty. Maximum 998 characters."New value: +"Subject line. The limit is the 998-octet header line, so a non-ASCII subject (RFC 2047 encoded) must be shorter in characters."

Previous value: -998New value: +989

Previous value: -"List of recipient email addresses. Each must be a valid RFC 5322 address. Maximum 50 recipients."New value: +"Recipient addresses."

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "inbox_id": {
+      "type": "string"
+    },
+    "notes": {
+      "description": "Server notes about how this call was handled — for example an argument that was not applied because the selected action does not accept it. Written by MCP Emails, not taken from any message, and absent when there is nothing to report.",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "total": {
+      "type": "integer"
+    }
+  },
+  "type": "object"
+}