download_unibox_attachment
Mint a short-lived download URL for one attachment on one message.
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Inputs are shown for personal API keys (bound) and for OAuth/delegated agents. Output schemas describe MCP structuredContent: native objects pass through; arrays, scalars and null use a data wrapper. Text content retains the native JSON result.
[Connect a client](/mcp/connect) · [Authentication and authorization](/authentication) · [Generated auth guide](/auth.md) · [Download tool catalog](/mcp-catalog.json) · [Agent documentation](/llms.txt)
## download_unibox_attachment
Mint a short-lived download URL for one attachment on one message.
Use when the attachment's contents are needed. Fetch it immediately: the URL expires, and it is deliberately not stored anywhere.
Do not pass the URL on or persist it — it is a bearer credential for customer mail with no further check behind it.
Scopes: unibox:read
Risk: read; confirmation: none; idempotency: none.
### Input schema (personal API key)
```json
{
"type": "object",
"properties": {
"workspaceId": {
"type": "string",
"pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|[fF]{8}-[fF]{4}-[fF]{4}-[fF]{4}-[fF]{12})$",
"format": "uuid"
},
"messageId": {
"type": "string",
"pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|[fF]{8}-[fF]{4}-[fF]{4}-[fF]{4}-[fF]{12})$",
"format": "uuid"
},
"attachmentId": {
"$ref": "#/$defs/AttachmentId"
}
},
"required": [
"workspaceId",
"messageId",
"attachmentId"
],
"patternProperties": {
"^(?!(?:workspaceId|messageId|attachmentId)$)[\\s\\S]*$": false
},
"additionalProperties": true,
"propertyNames": {
"type": "string",
"enum": [
"workspaceId",
"messageId",
"attachmentId"
]
},
"$defs": {
"AttachmentId": {
"type": "string",
"minLength": 1,
"maxLength": 512
}
}
}
```
### Input schema (OAuth / delegated agent)
```json
{
"type": "object",
"properties": {
"workspaceId": {
"type": "string",
"pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|[fF]{8}-[fF]{4}-[fF]{4}-[fF]{4}-[fF]{12})$",
"format": "uuid"
},
"messageId": {
"type": "string",
"pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|[fF]{8}-[fF]{4}-[fF]{4}-[fF]{4}-[fF]{12})$",
"format": "uuid"
},
"attachmentId": {
"$ref": "#/$defs/AttachmentId"
}
},
"required": [
"workspaceId",
"messageId",
"attachmentId"
],
"patternProperties": {
"^(?!(?:workspaceId|messageId|attachmentId)$)[\\s\\S]*$": false
},
"additionalProperties": true,
"propertyNames": {
"type": "string",
"enum": [
"workspaceId",
"messageId",
"attachmentId"
]
},
"$defs": {
"AttachmentId": {
"type": "string",
"minLength": 1,
"maxLength": 512
}
}
}
```
### Output schema (structuredContent)
```json
{
"type": "object",
"properties": {
"attachmentId": {
"$ref": "#/$defs/AttachmentId"
},
"url": {
"type": "string",
"minLength": 1,
"maxLength": 2048
},
"expiresAt": {
"$ref": "#/$defs/UtcDateTimeEncoded"
},
"filename": {
"$ref": "#/$defs/ShortText"
},
"contentType": {
"$ref": "#/$defs/ShortText"
},
"size": {
"type": "integer",
"minimum": 0,
"maximum": 9007199254740991
}
},
"required": [
"attachmentId",
"url",
"expiresAt",
"filename",
"contentType",
"size"
],
"patternProperties": {
"^(?!(?:attachmentId|url|expiresAt|filename|contentType|size)$)[\\s\\S]*$": false
},
"additionalProperties": true,
"propertyNames": {
"type": "string",
"enum": [
"attachmentId",
"url",
"expiresAt",
"filename",
"contentType",
"size"
]
},
"$defs": {
"AttachmentId": {
"type": "string",
"minLength": 1,
"maxLength": 512
},
"UtcDateTimeEncoded": {
"type": "string",
"pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}\\.\\d{3}Z$"
},
"ShortText": {
"type": "string",
"minLength": 1,
"maxLength": 256
}
}
}
```
### Underlying API operations
- `uniboxMessages.createAttachmentDownload`: `POST /v1/workspaces/:workspaceId/unibox/messages/:messageId/attachments/:attachmentId/download`