Fluxmail

Update draft

update_draft

DestructiveIdempotent

Replace all content of an existing email draft—recipients, subject, body, and attachments—to fully overwrite it, not patch it.

Instructions

Replace the content of an existing draft. This is a full replacement, not a patch.

Input Schema

Name	Required	Description
`cc`	No	Recipients, each "Name <a@x.com>" or "a@x.com"
`to`	No	Recipients, each "Name <a@x.com>" or "a@x.com"
`bcc`	No	Recipients, each "Name <a@x.com>" or "a@x.com"
`from`	No	Connected address or an available send-as address
`draftId`	Yes
`subject`	No	Defaults to "Re: ..." when replying
`bodyHtml`	No	HTML body
`bodyText`	No	Plain-text body. Line breaks appear in the sent email. Keep each prose paragraph on one continuous line and separate paragraphs with blank lines.
`replyAll`	No	With replyToMessageId: reply to all original recipients
`accountId`	No	Account to operate on. Optional when exactly one account is connected.
`attachments`	No
`replyToMessageId`	No	Message being replied to; threads correctly and computes recipients if "to" is omitted

Output Schema

Name	Required	Description	Default
`data`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed9 schema fields changedv0.19.0Oct 30, 2026

changedInput schema / properties / accountId / anyOf

Previous value: -[
-  {
-    "minLength": 1,
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "maxLength": 512,
+    "minLength": 1,
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / attachments / anyOf

Previous value: -[
-  {
-    "items": {
-      "additionalProperties": false,
-      "properties": {
-        "content": {
-          "description": "base64",
-          "type": "string"
-        },
-        "contentId": {
-          "description": "Content-ID for an inline image, referenced from bodyHtml as cid:<contentId>",
-          "minLength": 1,
-          "type": "string"
-        },
-        "disposition": {
-          "description": "Defaults to attachment",
-          "enum": [
-            "inline",
-            "attachment"
-          ],
-          "type": "string"
-        },
-        "filename": {
-          "minLength": 1,
-          "type": "string"
-        },
-        "mimeType": {
-          "minLength": 1,
-          "type": "string"
-        }
-      },
-      "required": [
-        "filename",
-        "mimeType",
-        "content"
-      ],
-      "type": "object"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "additionalProperties": false,
+      "properties": {
+        "content": {
+          "description": "base64",
+          "type": "string"
+        },
+        "contentId": {
+          "description": "Content-ID for an inline image, referenced from bodyHtml as cid:<contentId>",
+          "maxLength": 255,
+          "minLength": 1,
+          "type": "string"
+        },
+        "disposition": {
+          "description": "Defaults to attachment",
+          "enum": [
+            "inline",
+            "attachment"
+          ],
+          "type": "string"
+        },
+        "filename": {
+          "maxLength": 255,
+          "minLength": 1,
+          "type": "string"
+        },
+        "mimeType": {
+          "maxLength": 255,
+          "minLength": 1,
+          "type": "string"
+        }
+      },
+      "required": [
+        "filename",
+        "mimeType",
+        "content"
+      ],
+      "type": "object"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / bcc / anyOf

Previous value: -[
-  {
-    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
-    "items": {
-      "minLength": 1,
-      "type": "string"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "maxLength": 512,
+      "minLength": 1,
+      "type": "string"
+    },
+    "maxItems": 100,
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / cc / anyOf

Previous value: -[
-  {
-    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
-    "items": {
-      "minLength": 1,
-      "type": "string"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "maxLength": 512,
+      "minLength": 1,
+      "type": "string"
+    },
+    "maxItems": 100,
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / draftId / maxLength
```
Added value: +512
```

changedInput schema / properties / replyToMessageId / anyOf

Previous value: -[
-  {
-    "minLength": 1,
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "maxLength": 512,
+    "minLength": 1,
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / subject / anyOf

Added value: +[
+  {
+    "maxLength": 998,
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

removedInput schema / properties / subject / type
```
Removed value: -[
-  "string",
-  "null"
-]
```

changedInput schema / properties / to / anyOf

Previous value: -[
-  {
-    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
-    "items": {
-      "minLength": 1,
-      "type": "string"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "maxLength": 512,
+      "minLength": 1,
+      "type": "string"
+    },
+    "maxItems": 100,
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

Changed4 schema fields changedv0.18.0Oct 28, 2026

changedInput schema / properties / attachments / anyOf

Previous value: -[
-  {
-    "items": {
-      "additionalProperties": false,
-      "properties": {
-        "content": {
-          "description": "base64",
-          "type": "string"
-        },
-        "filename": {
-          "minLength": 1,
-          "type": "string"
-        },
-        "mimeType": {
-          "minLength": 1,
-          "type": "string"
-        }
-      },
-      "required": [
-        "filename",
-        "mimeType",
-        "content"
-      ],
-      "type": "object"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "additionalProperties": false,
+      "properties": {
+        "content": {
+          "description": "base64",
+          "type": "string"
+        },
+        "contentId": {
+          "description": "Content-ID for an inline image, referenced from bodyHtml as cid:<contentId>",
+          "minLength": 1,
+          "type": "string"
+        },
+        "disposition": {
+          "description": "Defaults to attachment",
+          "enum": [
+            "inline",
+            "attachment"
+          ],
+          "type": "string"
+        },
+        "filename": {
+          "minLength": 1,
+          "type": "string"
+        },
+        "mimeType": {
+          "minLength": 1,
+          "type": "string"
+        }
+      },
+      "required": [
+        "filename",
+        "mimeType",
+        "content"
+      ],
+      "type": "object"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / bcc / anyOf

Previous value: -[
-  {
-    "$ref": "#/properties/to/anyOf/0"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "minLength": 1,
+      "type": "string"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / cc / anyOf

Previous value: -[
-  {
-    "$ref": "#/properties/to/anyOf/0"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "minLength": 1,
+      "type": "string"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / replyToMessageId / anyOf

Previous value: -[
-  {
-    "$ref": "#/properties/draftId"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "minLength": 1,
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

Changed22 schema fields changedv0.15.0Oct 17, 2026

addedInput schema / properties / accountId / anyOf

Added value: +[
+  {
+    "minLength": 1,
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

removedInput schema / properties / accountId / minLength
```
Removed value: -1
```
removedInput schema / properties / accountId / type
```
Removed value: -"string"
```

addedInput schema / properties / attachments / anyOf

Added value: +[
+  {
+    "items": {
+      "additionalProperties": false,
+      "properties": {
+        "content": {
+          "description": "base64",
+          "type": "string"
+        },
+        "filename": {
+          "minLength": 1,
+          "type": "string"
+        },
+        "mimeType": {
+          "minLength": 1,
+          "type": "string"
+        }
+      },
+      "required": [
+        "filename",
+        "mimeType",
+        "content"
+      ],
+      "type": "object"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

removedInput schema / properties / attachments / items

Removed value: -{
-  "additionalProperties": false,
-  "properties": {
-    "content": {
-      "description": "base64",
-      "type": "string"
-    },
-    "filename": {
-      "minLength": 1,
-      "type": "string"
-    },
-    "mimeType": {
-      "minLength": 1,
-      "type": "string"
-    }
-  },
-  "required": [
-    "filename",
-    "mimeType",
-    "content"
-  ],
-  "type": "object"
-}

removedInput schema / properties / attachments / type
```
Removed value: -"array"
```
removedInput schema / properties / bcc / $ref
```
Removed value: -"#/properties/to"
```

addedInput schema / properties / bcc / anyOf

Added value: +[
+  {
+    "$ref": "#/properties/to/anyOf/0"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / bodyHtml / type

Previous value: -"string"New value: +[
+  "string",
+  "null"
+]

changedInput schema / properties / bodyText / type

Previous value: -"string"New value: +[
+  "string",
+  "null"
+]

removedInput schema / properties / cc / $ref
```
Removed value: -"#/properties/to"
```

addedInput schema / properties / cc / anyOf

Added value: +[
+  {
+    "$ref": "#/properties/to/anyOf/0"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / from / anyOf

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

removedInput schema / properties / from / format
```
Removed value: -"email"
```
removedInput schema / properties / from / type
```
Removed value: -"string"
```

changedInput schema / properties / replyAll / type

Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]

removedInput schema / properties / replyToMessageId / $ref
```
Removed value: -"#/properties/draftId"
```

addedInput schema / properties / replyToMessageId / anyOf

Added value: +[
+  {
+    "$ref": "#/properties/draftId"
+  },
+  {
+    "type": "null"
+  }
+]

changedInput schema / properties / subject / type

Previous value: -"string"New value: +[
+  "string",
+  "null"
+]

addedInput schema / properties / to / anyOf

Added value: +[
+  {
+    "description": "Recipients, each \"Name <a@x.com>\" or \"a@x.com\"",
+    "items": {
+      "minLength": 1,
+      "type": "string"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

removedInput schema / properties / to / items

Removed value: -{
-  "minLength": 1,
-  "type": "string"
-}

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

Changed1 schema field changedv0.11.1Oct 1, 2026
- removedOutput schema / $schema
```
Removed value: -"http://json-schema.org/draft-07/schema#"
```

Changed2 schema fields changedv0.11.0Sep 26, 2026

changedInput schema / properties / bodyText / description

Previous value: -"Plain-text body"New value: +"Plain-text body. Line breaks appear in the sent email. Keep each prose paragraph on one continuous line and separate paragraphs with blank lines."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "data": {
+      "additionalProperties": true,
+      "properties": {
+        "accountId": {
+          "type": "string"
+        },
+        "attachments": {
+          "items": {
+            "additionalProperties": true,
+            "properties": {
+              "filename": {
+                "type": "string"
+              },
+              "id": {
+                "type": "string"
+              },
+              "mimeType": {
+                "type": "string"
+              },
+              "sizeBytes": {
+                "type": "number"
+              }
+            },
+            "required": [
+              "id",
+              "filename",
+              "mimeType",
+              "sizeBytes"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "body": {
+          "additionalProperties": false,
+          "properties": {
+            "html": {
+              "type": "string"
+            },
+            "text": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "bodyTruncation": {
+          "additionalProperties": {
+            "additionalProperties": false,
+            "properties": {
+              "nextOffset": {
+                "type": "number"
+              },
+              "totalChars": {
+                "type": "number"
+              }
+            },
+            "required": [
+              "totalChars"
+            ],
+            "type": "object"
+          },
+          "type": "object"
+        },
+        "date": {
+          "type": "string"
+        },
+        "flags": {
+          "additionalProperties": true,
+          "properties": {
+            "draft": {
+              "type": "boolean"
+            },
+            "read": {
+              "type": "boolean"
+            },
+            "starred": {
+              "type": "boolean"
+            }
+          },
+          "required": [
+            "read",
+            "starred",
+            "draft"
+          ],
+          "type": "object"
+        },
+        "id": {
+          "type": "string"
+        },
+        "subject": {
+          "type": "string"
+        },
+        "threadId": {
+          "type": "string"
+        },
+        "to": {
+          "items": {
+            "additionalProperties": true,
+            "properties": {
+              "email": {
+                "type": "string"
+              },
+              "name": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "email"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        }
+      },
+      "required": [
+        "id",
+        "threadId",
+        "accountId",
+        "to",
+        "subject",
+        "date",
+        "flags"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "data"
+  ],
+  "type": "object"
+}

Changed1 schema field changedv0.9.0Sep 16, 2026

addedInput schema / properties / from

Added value: +{
+  "description": "Connected address or an available send-as address",
+  "format": "email",
+  "type": "string"
+}

First observedv0.1.0Jul 26, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already declare destructiveHint=true and idempotentHint=true, so the description is not carrying the safety profile alone. It still adds genuine value by clarifying that the operation is whole-object replacement, which tells the agent that omitted fields are effectively lost rather than preserved — a distinction the annotations do not convey.

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?

Two short sentences, front-loaded with the verb and the one behavioral caveat that matters. No filler and nothing that duplicates structured fields.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 12 parameters, an output schema, and rich annotations, the description covers the core semantics but leaves a consequential ambiguity unresolved: whether omitting a field (versus passing null) clears it, and whether attachments are dropped when not resent. For a destructive whole-object replace on an email draft, that gap matters.

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 83%, so the schema already explains recipients, bodyHtml/bodyText, attachments, and replyToMessageId in detail. The description contributes no parameter-level information beyond the general replacement semantics, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Replace the content of an existing draft') and adds a qualifier that separates it from a patch-style updater. It does not explicitly name siblings such as create_draft or get_draft, so the differentiation comes from the name rather than the prose.

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

Usage Guidelines3/5

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

'This is a full replacement, not a patch' implicitly tells the agent it must resend every field it wants to keep, which is real usage guidance. However, there is no explicit when-to-use versus create_draft/delete_draft, no note that draftId is required and must reference an existing draft, and no exclusion of drafts that have already been sent.

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