Commonpost MCP for Thunderbird

Save Draft

saveDraft

Save a composed email to the Drafts folder without sending or opening a compose window, or update an existing draft while keeping omitted fields unchanged.

Instructions

Save a composed message to the identity's Drafts folder without sending or opening a compose window, as the compose window does; returns messageId + folderPath, for the user to review and send later. With draftId, rewrite that draft instead: passed fields replace, omitted ones (body, recipients, attachments, reply headers) are kept, and the old version is removed.

Input Schema

Name	Required	Description
`cc`	No	CC recipients (comma-separated)
`to`	No	Recipient email address(es), comma-separated. Optional -- a draft can have no recipient.
`bcc`	No	BCC recipients (comma-separated)
`body`	No	Email body
`from`	No	Sender identity (email address or identity ID from listAccounts)
`isHtml`	No	Set to true if body contains HTML markup (default: false). With draftId the draft keeps its format; isHtml changes it only when the whole body is replaced
`draftId`	No	messageId of an existing draft to edit (from saveDraft, replyToMessage/forwardMessage mode draft, or a search in Drafts)
`subject`	No	Email subject line
`keepQuote`	No	With draftId and body: replace only the typed text, keeping cite line, quote, forwarded message and signature
`folderPath`	No	Drafts folder URI of draftId; searched in all Drafts folders when omitted
`attachments`	No	Attachments: file paths (strings) or inline objects ({name, contentType, base64})
`keepAttachments`	No	With draftId: keep the draft's attachments (new ones are added)

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv0.19.2Nov 5, 2026

changedInput schema / properties / attachments / items / oneOf

Previous value: -[
-  {
-    "description": "Absolute file path to attach",
-    "type": "string"
-  },
-  {
-    "additionalProperties": false,
-    "anyOf": [
-      {
-        "required": [
-          "base64"
-        ],
-        "type": "object"
-      },
-      {
-        "required": [
-          "content"
-        ],
-        "type": "object"
-      }
-    ],
-    "properties": {
-      "base64": {
-        "contentEncoding": "base64",
-        "description": "Base64-encoded file content",
-        "minLength": 1,
-        "type": "string"
-      },
-      "content": {
-        "contentEncoding": "base64",
-        "description": "Alias for base64 (accepted for backwards compatibility); base64 takes precedence when both are set",
-        "minLength": 1,
-        "type": "string"
-      },
-      "contentType": {
-        "description": "MIME type, e.g. application/pdf",
-        "type": "string"
-      },
-      "name": {
-        "description": "Attachment filename",
-        "minLength": 1,
-        "type": "string"
-      }
-    },
-    "required": [
-      "name"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "description": "Absolute file path",
+    "type": "string"
+  },
+  {
+    "additionalProperties": false,
+    "anyOf": [
+      {
+        "required": [
+          "base64"
+        ],
+        "type": "object"
+      },
+      {
+        "required": [
+          "content"
+        ],
+        "type": "object"
+      }
+    ],
+    "properties": {
+      "base64": {
+        "contentEncoding": "base64",
+        "description": "File content, base64",
+        "minLength": 1,
+        "type": "string"
+      },
+      "content": {
+        "contentEncoding": "base64",
+        "description": "Old name of base64, which wins if both are set",
+        "minLength": 1,
+        "type": "string"
+      },
+      "contentType": {
+        "description": "MIME type",
+        "type": "string"
+      },
+      "name": {
+        "description": "File name",
+        "minLength": 1,
+        "type": "string"
+      }
+    },
+    "required": [
+      "name"
+    ],
+    "type": "object"
+  }
+]

changedInput schema / properties / body / description

Previous value: -"Email body (optional)"New value: +"Email body"

changedInput schema / properties / subject / description

Previous value: -"Email subject line (optional)"New value: +"Email subject line"

removedInput schema / required
```
Removed value: -[]
```

First observedv0.1.0Nov 5, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare non-read-only, non-destructive, non-idempotent, closed-world; the description adds substantive behavior on top: nothing is sent, no compose UI opens, messageId and folderPath are returned, and editing a draft disposes of the prior version while preserving omitted fields. It does not cover auth or identity-resolution requirements, keeping it below the top score.

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?

Two sentences, front-loaded with the core action and then the draftId variant, with no padding or restatement of the name. The clause 'without sending or opening a compose window, as the compose window does' is mildly redundant in its phrasing but still carries disambiguation value.

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 a 12-parameter tool with no output schema, the description covers the return shape (messageId + folderPath), the create-versus-edit mode split, and merge semantics on edit. Remaining detail — attachment count limits, folderPath fallback search, isHtml interaction — is already documented at 100% schema coverage, so nothing critical is missing.

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 field-level meanings are already covered, but the description adds cross-parameter semantics the schema cannot express: passed fields replace while omitted ones (body, recipients, attachments, reply headers) are kept, and the old version is removed. That merge-versus-replace rule is the single most important thing an agent needs and it comes from the description, not the schema.

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 (save a composed message to the Drafts folder) plus the negative scope that distinguishes it from sending and from the compose window, and names the return values. The second sentence carves out the distinct edit mode with draftId, so an agent can tell both modes apart from sendMail 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?

Provides clear usage context — save for review and send later, and use draftId when rewriting an existing draft rather than creating a new one. It stops short of naming the sibling alternative explicitly (e.g. 'use sendMail when the user wants it delivered now'), so the routing is implied rather than spelled out.

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

Save Draft

Instructions

Input Schema

Schema Changelog

TDQS

Other Tools