# MCP tool reference

1 callable tools.

Use tools/call at https://mcp.schedulerzero.com/mcp with the exact tool name and arguments below. The /tools/ paths in this view are documentation identifiers, not HTTP endpoints. Request execution is disabled for this reference.

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`