Google Workspace MCP Server - Control Gmail, Calendar, Docs, Sheets, Slides, Chat, Forms & Drive

Send Gmail Message

send_gmail_message

Send Gmail messages instantly with support for new emails, replies, forwards, attachments, and sending from alias addresses. Uses your authenticated Google Workspace account.

Instructions

Sends an email using the user's Gmail account. Supports new emails, replies, and forwards, with optional attachments. Supports Gmail's "Send As" feature to send from configured alias addresses.

To forward an existing message, pass forward_message_id. The original subject, body (quoted with a "Forwarded message" header), and attachments are carried over. In forward mode, body (if any) is prepended as a note and subject is optional. Threading, reply, and signature options do not apply when forwarding.

THIS TOOL SENDS IMMEDIATELY AND CANNOT SCHEDULE. Gmail's REST API exposes no send-time parameter; Schedule send is a web-UI feature with no API equivalent, so no argument to this tool can defer delivery. Never tell a user a message was scheduled. For "prepare now, deliver later", create a draft with draft_gmail_message. An external scheduler must retain the message data to create and send a new message via send_gmail_message at the chosen time, or call users.drafts.send with the draft ID returned by draft_gmail_message. Alternatively, let the user schedule that draft in the Gmail UI.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`cc`	No	Optional CC email address.
`to`	No	Recipient email address. Optional when replying with reply_all=True, which derives it from the thread.
`bcc`	No	Optional BCC email address.
`body`	No	Email body content (plain text or HTML). Required when sending. When forwarding, this is an optional note prepended above the quoted original.
`subject`	No	Email subject. Required when sending; optional when forwarding (defaults to 'Fwd: <original subject>').
`from_name`	No	Optional sender display name (e.g., 'Peter Hartree'). If provided, the From header will be formatted as 'Name <email>'.
`reply_all`	No	Whether to derive reply-all recipients from the thread: To = the sender being replied to, Cc = the other participants, excluding the authenticated account and from_email. Requires thread_id. Explicit to/cc win; when cc is omitted the sender being replied to is added to the derived Cc if they are not already in To. Defaults to false.
`thread_id`	No	Optional Gmail thread ID to reply within. When in_reply_to is omitted, replies to the latest non-draft, non-trash message with an RFC Message-ID.
`from_email`	No	Optional 'Send As' alias email address. Must be configured in Gmail settings (Settings > Accounts > Send mail as). If not provided, uses the authenticated user's email.
`references`	No	Optional Message-ID ancestry chain. Normally omit when thread_id is provided; the server derives the chain through the selected reply target.
`attachments`	No	Optional list of attachments. Each can have: "url" (fetch from URL — works with MCP attachment URLs from get_drive_file_download_url / get_gmail_attachment_content), OR "path" (file path, auto-encodes), OR "content" (standard base64, not urlsafe) + "filename". Optional "mime_type". Optional "content_id" (string) makes the attachment inline-rendered: it lands in a multipart/related part with `Content-ID: <content_id>` and `Content-Disposition: inline`, and the HTML body can reference it via `<img src="cid:<content_id>">` (RFC 2392). Without `content_id` the attachment is a regular multipart/mixed attachment. Example: [{"url": "https://host/attachments/abc-123", "filename": "report.pdf"}]
`body_format`	No	Format of the body content (and of the prepended note when forwarding). Use 'plain' for plaintext or 'html' for HTML content.	plain
`in_reply_to`	No	Optional RFC Message-ID to explicitly reply to a specific message (e.g., '<message123@gmail.com>'). Omit to reply to the latest eligible message in thread_id.
`quote_original`	No	Whether to include the message being replied to as a quoted original. Only has an effect when thread_id is provided. Defaults to false.
`include_signature`	No	Whether to append the Gmail signature from Settings > Signature when available. Defaults to true.
`user_google_email`	Yes	The user's Google email address. Required for authentication.
`forward_message_id`	No	Set to a Gmail message ID to forward that message instead of composing a new one. The original subject, body, and (optionally) attachments are carried over; 'body' becomes an optional note prepended to the forward.
`include_forwarded_attachments`	No	When forwarding, whether to include the original message's attachments. Ignored unless forward_message_id is set.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed25 schema fields changedv1.28.0Sep 24, 2026

removedInput schema / properties / attachments / anyOf

Removed value: -[
-  {
-    "items": {
-      "additionalProperties": true,
-      "type": "object"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / attachments / items

Added value: +{
+  "additionalProperties": true,
+  "type": "object"
+}

addedInput schema / properties / attachments / type
```
Added value: +"array"
```

removedInput schema / properties / bcc / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / bcc / type
```
Added value: +"string"
```

removedInput schema / properties / body / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / body / type
```
Added value: +"string"
```

removedInput schema / properties / cc / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / cc / type
```
Added value: +"string"
```

removedInput schema / properties / forward_message_id / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / forward_message_id / type
```
Added value: +"string"
```

removedInput schema / properties / from_email / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / from_email / type
```
Added value: +"string"
```

removedInput schema / properties / from_name / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / from_name / type
```
Added value: +"string"
```

removedInput schema / properties / in_reply_to / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / in_reply_to / type
```
Added value: +"string"
```

removedInput schema / properties / references / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / references / type
```
Added value: +"string"
```

removedInput schema / properties / subject / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / subject / type
```
Added value: +"string"
```

removedInput schema / properties / thread_id / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / thread_id / type
```
Added value: +"string"
```

removedInput schema / properties / to / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / to / type
```
Added value: +"string"
```

Changed3 schema fields changedv1.25.2Aug 30, 2026

changedInput schema / properties / in_reply_to / description

Previous value: -"Optional RFC Message-ID of the message being replied to (e.g., '<message123@gmail.com>')."New value: +"Optional RFC Message-ID to explicitly reply to a specific message (e.g., '<message123@gmail.com>'). Omit to reply to the latest eligible message in thread_id."

changedInput schema / properties / references / description

Previous value: -"Optional chain of Message-IDs for proper threading."New value: +"Optional Message-ID ancestry chain. Normally omit when thread_id is provided; the server derives the chain through the selected reply target."

changedInput schema / properties / thread_id / description

Previous value: -"Optional Gmail thread ID to reply within."New value: +"Optional Gmail thread ID to reply within. When in_reply_to is omitted, replies to the latest non-draft, non-trash message with an RFC Message-ID."

Changed7 schema fields changedv1.24.0Aug 13, 2026

addedInput schema / properties / quote_original

Added value: +{
+  "default": false,
+  "description": "Whether to include the message being replied to as a quoted original. Only has an effect when thread_id is provided. Defaults to false.",
+  "type": "boolean"
+}

addedInput schema / properties / reply_all

Added value: +{
+  "default": false,
+  "description": "Whether to derive reply-all recipients from the thread: To = the sender being replied to, Cc = the other participants, excluding the authenticated account and from_email. Requires thread_id. Explicit to/cc win; when cc is omitted the sender being replied to is added to the derived Cc if they are not already in To. Defaults to false.",
+  "type": "boolean"
+}

addedInput schema / properties / to / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / to / default
```
Added value: +null
```

changedInput schema / properties / to / description

Previous value: -"Recipient email address."New value: +"Recipient email address. Optional when replying with reply_all=True, which derives it from the thread."

removedInput schema / properties / to / type
```
Removed value: -"string"
```

changedInput schema / required

Previous value: -[
-  "user_google_email",
-  "to"
-]New value: +[
+  "user_google_email"
+]

Changed30 schema fields changedv1.0.1Jul 31, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

addedInput schema / properties / attachments

Added value: +{
+  "anyOf": [
+    {
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional list of attachments. Each can have: \"url\" (fetch from URL — works with MCP attachment URLs from get_drive_file_download_url / get_gmail_attachment_content), OR \"path\" (file path, auto-encodes), OR \"content\" (standard base64, not urlsafe) + \"filename\". Optional \"mime_type\". Optional \"content_id\" (string) makes the attachment inline-rendered: it lands in a multipart/related part with `Content-ID: <content_id>` and `Content-Disposition: inline`, and the HTML body can reference it via `<img src=\"cid:<content_id>\">` (RFC 2392). Without `content_id` the attachment is a regular multipart/mixed attachment. Example: [{\"url\": \"https://host/attachments/abc-123\", \"filename\": \"report.pdf\"}]"
+}

addedInput schema / properties / bcc

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional BCC email address."
+}

addedInput schema / properties / body / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / body / default
```
Added value: +null
```

changedInput schema / properties / body / description

Previous value: -"Email body (plain text)."New value: +"Email body content (plain text or HTML). Required when sending. When forwarding, this is an optional note prepended above the quoted original."

removedInput schema / properties / body / title
```
Removed value: -"Body"
```
removedInput schema / properties / body / type
```
Removed value: -"string"
```

addedInput schema / properties / body_format

Added value: +{
+  "default": "plain",
+  "description": "Format of the body content (and of the prepended note when forwarding). Use 'plain' for plaintext or 'html' for HTML content.",
+  "enum": [
+    "plain",
+    "html"
+  ],
+  "type": "string"
+}

addedInput schema / properties / cc

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional CC email address."
+}

addedInput schema / properties / forward_message_id

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Set to a Gmail message ID to forward that message instead of composing a new one. The original subject, body, and (optionally) attachments are carried over; 'body' becomes an optional note prepended to the forward."
+}

addedInput schema / properties / from_email

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional 'Send As' alias email address. Must be configured in Gmail settings (Settings > Accounts > Send mail as). If not provided, uses the authenticated user's email."
+}

addedInput schema / properties / from_name

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional sender display name (e.g., 'Peter Hartree'). If provided, the From header will be formatted as 'Name <email>'."
+}

addedInput schema / properties / in_reply_to

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional RFC Message-ID of the message being replied to (e.g., '<message123@gmail.com>')."
+}

addedInput schema / properties / include_forwarded_attachments

Added value: +{
+  "default": true,
+  "description": "When forwarding, whether to include the original message's attachments. Ignored unless forward_message_id is set.",
+  "type": "boolean"
+}

addedInput schema / properties / include_signature

Added value: +{
+  "default": true,
+  "description": "Whether to append the Gmail signature from Settings > Signature when available. Defaults to true.",
+  "type": "boolean"
+}

addedInput schema / properties / references

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional chain of Message-IDs for proper threading."
+}

removedInput schema / properties / service

Removed value: -{
-  "title": "service",
-  "type": "string"
-}

addedInput schema / properties / subject / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / subject / default
```
Added value: +null
```

changedInput schema / properties / subject / description

Previous value: -"Email subject."New value: +"Email subject. Required when sending; optional when forwarding (defaults to 'Fwd: <original subject>')."

removedInput schema / properties / subject / title
```
Removed value: -"Subject"
```
removedInput schema / properties / subject / type
```
Removed value: -"string"
```

addedInput schema / properties / thread_id

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Optional Gmail thread ID to reply within."
+}

removedInput schema / properties / to / title
```
Removed value: -"To"
```

addedInput schema / properties / user_google_email / description

Added value: +"The user's Google email address. Required for authentication."

removedInput schema / properties / user_google_email / title
```
Removed value: -"User Google Email"
```

changedInput schema / required

Previous value: -[
-  "service",
-  "user_google_email",
-  "to",
-  "subject",
-  "body"
-]New value: +[
+  "user_google_email",
+  "to"
+]

removedInput schema / title

Removed value: -"send_gmail_messageArguments"

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "result": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object",
+  "x-fastmcp-wrap-result": true
+}

First observedv1.0.0Jun 10, 2025

TDQS

A4.7/5.0

Behavior5/5

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

Despite annotations indicating readOnlyHint=false and idempotentHint=false, the description goes far beyond them by disclosing the immediate-send behavior, the absence of any API scheduling parameter, and the exact consequences for external schedulers. It also explains forward-mode behavior (subject/body/attachments carried over) and which options do not apply when forwarding. This is rich behavioral context that annotations alone cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is long (about 13 sentences), but nearly every sentence earns its place, especially the emphatic scheduling warning and the forward-mode semantics. It is front-loaded with the core purpose and the most critical operational constraint. The length is justified by the tool's complexity (18 parameters, three modes), though a slightly tighter wording could earn a 5.

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?

For an 18-parameter send tool with new/reply/forward modes and a major scheduling caveat, the description covers the key decision points: what the tool does, when to use draft_gmail_message instead, and how forwarding alters parameter semantics. The output schema exists, so the absence of return-value details is acceptable. Only minor omissions (e.g., permission requirements, rate limits) prevent a perfect score.

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?

Schema coverage is 100%, so the baseline is 3, but the description adds cross-parameter meaning: in forward mode, body becomes a prepended note and subject becomes optional; threading/reply/signature options are inert when forwarding. This goes beyond the individual parameter descriptions in the schema. It stops short of methodically walking through every parameter interaction, but it adds substantial value for the most complex mode (forward).

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 opens with a precise verb and resource: 'Sends an email using the user's Gmail account.' It then lists supported modes (new, reply, forward, attachments, Send As), which clearly distinguishes it from the sibling draft_gmail_message and other Gmail read/label tools. The scope is immediately recognizable and unambiguous.

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?

The description explicitly tells agents when NOT to use this tool: scheduling is impossible, and for 'prepare now, deliver later' it names the alternative draft_gmail_message. It also states a hard rule, 'Never tell a user a message was scheduled', preventing a common hallucination. This is exactly the kind of when-to-use / when-not-to-use guidance that is usually missing.

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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