MCP Emails

Save an edited draft

draft_editor_save

Idempotent

Save the fields a person edited in the draft editor. Every field is optional and an omitted one keeps its stored value. No signature is applied, unlike the draft tool's 'update' when it is given a body: the text being saved is the text the person was shown, which already carries one if the inbox has one. Nothing is sent. On IMAP the save returns a NEW draft_id and the old one stops resolving. On IMAP and Gmail the save rebuilds the message from its text, so a draft with attachments, inline images other than its own signature images, or other extra parts is refused and left unchanged. A save against an older id of the draft, or against a revision other than base_revision, is refused as draft_changed and nothing is written.

Input Schema

TableJSON Schema

Name	Required	Description
`cc`	No	Replacement recipient list. Omit to keep the stored one; pass [] to clear it.
`to`	No	Replacement recipient list. Omit to keep the stored one; pass [] to clear it.
`bcc`	No	Replacement recipient list. Omit to keep the stored one; pass [] to clear it.
`inbox`	No	The inbox's email address, as an alternative to inbox_id.
`subject`	No	Replacement subject line. Omit to keep the stored one.
`draft_id`	Yes	The draft to act on. On IMAP a draft_id changes on every save, so use the one the most recent draft result returned.
`inbox_id`	No	The inbox holding the draft. Omit when the workspace has one inbox.
`body_text`	No	Replacement plain-text body, written exactly as given. When the draft has an HTML part, the edit is made inside it when it can be placed exactly; otherwise a formatted HTML part is dropped (body.formatting_removed) and a plain one is regenerated, so both parts of the message say the same thing. Omit to keep the stored body.
`base_revision`	No	The draft.revision of the copy being edited (0 when it had none). When the draft has been rewritten since, the save is refused as draft_changed.
`add_attachments`	No	Files to add, base64. The stored files are kept. 10 MB in all per save.
`remove_attachments`	No	Stored files to remove, by position in draft.attachments, each naming the file it means. Every other file is kept byte for byte. Refused as draft_changed when the file at that position is another one, and on Outlook, where a save cannot remove one.

Output Schema

TableJSON Schema

Name	Required	Description
`card`	No	Which card this envelope renders: 'draft_editor' or 'receipt'.
`state`	No	Where the draft stands: editing, sent, cancelled (discarded, or the card was hidden or shown), or error.
`dashboard_url`	No	Absolute link to the signed-in dashboard. Always present, and the one link that still works when the rest of the envelope cannot be parsed.
`schema_version`	No	Card envelope version. A client that does not know this version should fall back to dashboard_url.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 17, 2026

addedInput schema / properties / add_attachments

Added value: +{
+  "description": "Files to add, base64. The stored files are kept. 10 MB in all per save.",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "data": {
+        "description": "Standard base64.",
+        "type": "string"
+      },
+      "filename": {
+        "type": "string"
+      },
+      "mime_type": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "filename",
+      "mime_type",
+      "data"
+    ],
+    "type": "object"
+  },
+  "maxItems": 20,
+  "type": "array"
+}

changedInput schema / properties / body_text / description

Previous value: -"Replacement plain-text body, written exactly as given. When the draft has an HTML part it is regenerated from this text, so both parts of the message say the same thing. Omit to keep the stored body."New value: +"Replacement plain-text body, written exactly as given. When the draft has an HTML part, the edit is made inside it when it can be placed exactly; otherwise a formatted HTML part is dropped (body.formatting_removed) and a plain one is regenerated, so both parts of the message say the same thing. Omit to keep the stored body."

addedInput schema / properties / remove_attachments

Added value: +{
+  "description": "Stored files to remove, by position in draft.attachments, each naming the file it means. Every other file is kept byte for byte. Refused as draft_changed when the file at that position is another one, and on Outlook, where a save cannot remove one.",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "filename": {
+        "type": "string"
+      },
+      "index": {
+        "minimum": 0,
+        "type": "integer"
+      },
+      "size_bytes": {
+        "minimum": 0,
+        "type": [
+          "integer",
+          "null"
+        ]
+      }
+    },
+    "required": [
+      "index",
+      "filename"
+    ],
+    "type": "object"
+  },
+  "maxItems": 20,
+  "type": "array"
+}

Changed1 schema field changedOct 15, 2026

changedOutput schema / properties / state / description

Previous value: -"Where the draft stands: editing, sent, or error."New value: +"Where the draft stands: editing, sent, cancelled (discarded, or the card was hidden or shown), or error."

Changed1 schema field changedOct 13, 2026

addedInput schema / properties / base_revision

Added value: +{
+  "description": "The draft.revision of the copy being edited (0 when it had none). When the draft has been rewritten since, the save is refused as draft_changed.",
+  "minimum": 0,
+  "type": "integer"
+}

AddedSep 16, 2026

TDQS

A3.6/5.0

Behavior1/5

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

The annotations declare idempotentHint=true, but the description says on IMAP the save returns a NEW draft_id and the old one stops resolving, so an identical repeated call would not have the same effect. This contradicts the annotation and triggers the annotation-contradiction rule despite the description otherwise adding rich behavioral detail.

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 dense but front-loads the purpose and proceeds through important caveats. Every sentence carries useful behavioral information, though the paragraph could be slightly tightened.

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?

For a complex save operation across IMAP, Gmail, and Outlook, the description covers no-signature behavior, no sending, new draft_id behavior, rebuild limitations, and refusal conditions. With an output schema present, it need not explain return values.

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 each parameter's meaning, including omit-to-keep semantics. The description adds only a blanket optionality rule, which is largely duplicative and slightly imprecise against the required draft_id.

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?

States a specific verb and resource: saving fields edited in the draft editor. It distinguishes from the draft tool's update behavior and clarifies that nothing is sent, so an agent can identify its role without opening the schema.

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?

Gives clear context: use it after a person edits a draft in the draft editor. It also contrasts with the draft tool's update when a body is supplied, but does not explicitly enumerate alternatives or when-not-to-use beyond refusal cases.

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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