Fastmail MCP Server

Instructions

Implementation Reference

• src/index.ts:953-968 (handler)

  MCP tool handler for 'move_email': validates input parameters, initializes JmapClient, calls client.moveEmail, and returns success response.

  case 'move_email': {
    const { emailId, targetMailboxId } = args as any;
    if (!emailId || !targetMailboxId) {
      throw new McpError(ErrorCode.InvalidParams, 'emailId and targetMailboxId are required');
    }
    const client = initializeClient();
    await client.moveEmail(emailId, targetMailboxId);
    return {
      content: [
        {
          type: 'text',
          text: 'Email moved successfully',
        },
      ],
    };
  }

• src/index.ts:435-451 (schema)

  Input schema and registration for the 'move_email' tool in the ListTools response.

    name: 'move_email',
    description: 'Move an email to a different mailbox',
    inputSchema: {
      type: 'object',
      properties: {
        emailId: {
          type: 'string',
          description: 'ID of the email to move',
        },
        targetMailboxId: {
          type: 'string',
          description: 'ID of the target mailbox',
        },
      },
      required: ['emailId', 'targetMailboxId'],
    },
  },

• src/jmap-client.ts:398-424 (handler)

  Core JmapClient method implementing email move via JMAP Email/set with updated mailboxIds.

  async moveEmail(emailId: string, targetMailboxId: string): Promise<void> {
    const session = await this.getSession();
  
    const targetMailboxIds: Record<string, boolean> = {};
    targetMailboxIds[targetMailboxId] = true;
  
    const request: JmapRequest = {
      using: ['urn:ietf:params:jmap:core', 'urn:ietf:params:jmap:mail'],
      methodCalls: [
        ['Email/set', {
          accountId: session.accountId,
          update: {
            [emailId]: {
              mailboxIds: targetMailboxIds
            }
          }
        }, 'moveEmail']
      ]
    };
  
    const response = await this.makeRequest(request);
    const result = response.methodResponses[0][1];
    
    if (result.notUpdated && result.notUpdated[emailId]) {
      throw new Error('Failed to move email.');
    }
  }

• src/index.ts:1140-1140 (registration)

  Tool name listed in check_function_availability response for email functions.

  'get_recent_emails', 'mark_email_read', 'delete_email', 'move_email',