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Albretsen

MCP Emails

by Albretsen
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Hybrid

Scheduled Send

schedule

Queue email messages for delivery at a future time, or cancel a pending scheduled send before it goes out.

Instructions

Queue a message from one inbox for delivery at a future time, or cancel one that is queued. Use email_compose to send now; use this only when the user names a later time. send_at is an ISO 8601 timestamp WITH a timezone offset ("2026-06-02T09:00:00+02:00" or a trailing Z), in the future; the server dispatches within about 60 seconds of it, so it is not for second-precise timing. Recipients and body are validated at create time and an invalid message is never queued. Attachments here are inline base64 { filename, mime_type, data } only, 10 MB total; the { source_message_id, attachment_index } reference form belongs to email_compose. Only a send still 'pending' can be cancelled; use schedule_list to see what is queued and to get the id that 'cancel' takes. Every action needs the schedule:email scope. A cancel result is your own queued data, not mailbox content, so it carries no untrusted_content flag.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
ccNoCc addresses.
idNoScheduled send UUID from a create or list call.
toNoRecipient addresses.
bccNoBcc addresses.
bodyNoPlain-text body. Sent as multipart/alternative when html_body is given too.
inboxNoInbox email address, an alternative to inbox_id.
actionYesOperation to run. create = queue to, subject and body for send_at; cancel = a pending send by `id`.
send_atNoSend 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.
subjectNoSubject line. The limit is the 998-octet header line, so a non-ASCII subject (RFC 2047 encoded) must be shorter in characters.
inbox_idNoInbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both.
reply_toNoReply-To address.
html_bodyNoOptional HTML body.
attachmentsNoFile attachments, 10 MB total. Inline base64 only here — the { source_message_id, attachment_index } reference form is email_compose's, not this tool's.
idempotency_keyNoReuse only when retrying the identical request within 24 hours; the retry is collapsed, not repeated. Reuse with different arguments is rejected.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
notesNoServer 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.
totalNo
inbox_idNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed13 schema fields changed
    • removedInput schema / allOf
      Removed value: -[
-  {
-    "if": {
-      "properties": {
-        "action": {
-          "const": "create"
-        }
-      },
-      "required": [
-        "action"
-      ]
-    },
-    "then": {
-      "not": {
-        "anyOf": [
-          {
-            "required": [
-              "limit"
-            ]
-          },
-          {
-            "required": [
-              "id"
-            ]
-          },
-          {
-            "required": [
-              "scheduled_send_id"
-            ]
-          }
-        ]
-      },
-      "required": [
-        "to",
-        "subject",
-        "body",
-        "send_at"
-      ]
-    }
-  },
-  {
-    "if": {
-      "properties": {
-        "action": {
-          "const": "list"
-        }
-      },
-      "required": [
-        "action"
-      ]
-    },
-    "then": {
-      "not": {
-        "anyOf": [
-          {
-            "required": [
-              "inbox"
-            ]
-          },
-          {
-            "required": [
-              "to"
-            ]
-          },
-          {
-            "required": [
-              "cc"
-            ]
-          },
-          {
-            "required": [
-              "bcc"
-            ]
-          },
-          {
-            "required": [
-              "subject"
-            ]
-          },
-          {
-            "required": [
-              "body"
-            ]
-          },
-          {
-            "required": [
-              "html_body"
-            ]
-          },
-          {
-            "required": [
-              "attachments"
-            ]
-          },
-          {
-            "required": [
-              "reply_to"
-            ]
-          },
-          {
-            "required": [
-              "send_at"
-            ]
-          },
-          {
-            "required": [
-              "idempotency_key"
-            ]
-          },
-          {
-            "required": [
-              "id"
-            ]
-          },
-          {
-            "required": [
-              "scheduled_send_id"
-            ]
-          }
-        ]
-      }
-    }
-  },
-  {
-    "if": {
-      "properties": {
-        "action": {
-          "const": "cancel"
-        }
-      },
-      "required": [
-        "action"
-      ]
-    },
-    "then": {
-      "not": {
-        "anyOf": [
-          {
-            "required": [
-              "inbox_id"
-            ]
-          },
-          {
-            "required": [
-              "inbox"
-            ]
-          },
-          {
-            "required": [
-              "to"
-            ]
-          },
-          {
-            "required": [
-              "cc"
-            ]
-          },
-          {
-            "required": [
-              "bcc"
-            ]
-          },
-          {
-            "required": [
-              "subject"
-            ]
-          },
-          {
-            "required": [
-              "body"
-            ]
-          },
-          {
-            "required": [
-              "html_body"
-            ]
-          },
-          {
-            "required": [
-              "attachments"
-            ]
-          },
-          {
-            "required": [
-              "reply_to"
-            ]
-          },
-          {
-            "required": [
-              "send_at"
-            ]
-          },
-          {
-            "required": [
-              "idempotency_key"
-            ]
-          },
-          {
-            "required": [
-              "limit"
-            ]
-          }
-        ]
-      }
-    }
-  }
-]
    • changedInput schema / properties / action / description
      Previous value: -"Operation to run. create = queue to, subject and body for send_at; list = pending scheduled sends; cancel = a pending send by `id`, alias `scheduled_send_id`."New value: +"Operation to run. create = queue to, subject and body for send_at; cancel = a pending send by `id`."
    • changedInput schema / properties / action / enum
      Previous value: -[
-  "create",
-  "list",
-  "cancel"
-]New value: +[
+  "create",
+  "cancel"
+]
    • changedInput schema / properties / attachments / description
      Previous value: -"File attachments, 10 MB total."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."
    • changedInput schema / properties / id / description
      Previous value: -"Scheduled send UUID from a create or list call. Alias: scheduled_send_id."New value: +"Scheduled send UUID from a create or list call."
    • changedInput schema / properties / idempotency_key / description
      Previous value: -"Opaque key for one operation, outbound or mailbox mutation. Reuse it only when retrying the identical request within 24 hours: the retry is collapsed, not repeated, which matters most for copy. Reuse with different arguments is rejected; omit it for normal behaviour."New value: +"Reuse only when retrying the identical request within 24 hours; the retry is collapsed, not repeated. Reuse with different arguments is rejected."
    • changedInput schema / properties / inbox / description
      Previous value: -"Inbox email address; an alternative to inbox_id, which wins when both are given."New value: +"Inbox email address, an alternative to inbox_id."
    • changedInput schema / properties / inbox_id / description
      Previous value: -"Inbox UUID. Optional when the key has exactly one inbox. Otherwise pass this or `inbox`; omit both and the error lists every inbox_id."New value: +"Inbox UUID from inbox_list. Optional when the key has one inbox; pass this or `inbox`, not both."
    • removedInput schema / properties / limit
      Removed value: -{
-  "default": 20,
-  "description": "Results per page.",
-  "maximum": 100,
-  "minimum": 1,
-  "type": "integer"
-}
    • removedInput schema / properties / scheduled_send_id
      Removed value: -{
-  "description": "Alias of `id`; pass either one.",
-  "format": "uuid",
-  "type": "string"
-}
    • changedInput schema / properties / subject / description
      Previous value: -"Subject line."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."
    • changedInput schema / properties / subject / maxLength
      Previous value: -998New value: +989
    • changedOutput schema / (root)
      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"
+}
  2. First observedv1.0.4

TDQS

A5/5.0
Behavior5/5

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

Annotations provide readOnlyHint=false and destructiveHint=false, but the description adds rich behavioral detail: send_at must be in the future with a timezone offset, delivery can be up to 60s late (not second-precise), recipients/body are validated at create time, invalid messages never queued, attachments are inline base64 only (not the reference form), cancellations return queued data (no untrusted_content flag), and the schedule:email scope requirement. This exceeds the baseline and adds significant value beyond annotations.

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?

The description is a single, dense paragraph that is front-loaded with the core purpose and usage guidance, then adds critical behavioral constraints. Every sentence adds value; there is no fluff. It is concise given the tool's complexity (nine action-specific parameters, multiple modes).

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?

Given the tool's complexity (14 parameters, two actions, multiple constraints like timezone, attachment format, cancellation rules), the description covers all critical aspects: action selection, validation, delivery timing, attachment format, cancellation prerequisites, scheduler reference, and scopes. The output schema exists but is not needed to understand behavior. It is complete for correct invocation; no critical information is missing.

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

Parameters5/5

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

Although schema description coverage is 100%, the description provides critical semantics that the schema does not: send_at must be in the future with timezone offset and has up-to-60s delivery delay; attachments are inline base64 only (not the reference form) and 10 MB total; idempotency_key reuse is collapsed only when retrying identical requests; non-ASCII subject length constraint. These are essential for correct invocation and go beyond the parameter names.

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?

The description states a specific verb ('Queue a message... for delivery at a future time, or cancel one that is queued') and names the resource (message from one inbox). It distinguishes from email_compose by saying 'Use email_compose to send now; use this only when the user names a later time.' This clearly differentiates the tool from its main sibling.

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

Usage Guidelines5/5

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

It explicitly says when to use the tool ('use this only when the user names a later time') and names the alternative (email_compose). It also specifies the conditions for cancellation ('Only a send still 'pending' can be cancelled') and references schedule_list for seeing queued items and getting the id. This gives clear context and exclusions.

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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