Fastmail MCP Server

Instructions

Implementation Reference

• src/jmap-client.ts:426-443 (handler)

  Core handler function that executes the tool logic by making a JMAP Email/get request to retrieve attachments for the specified email ID.

  async getEmailAttachments(emailId: string): Promise<any[]> {
    const session = await this.getSession();
  
    const request: JmapRequest = {
      using: ['urn:ietf:params:jmap:core', 'urn:ietf:params:jmap:mail'],
      methodCalls: [
        ['Email/get', {
          accountId: session.accountId,
          ids: [emailId],
          properties: ['attachments']
        }, 'getAttachments']
      ]
    };
  
    const response = await this.makeRequest(request);
    const email = response.methodResponses[0][1].list[0];
    return email?.attachments || [];
  }

• src/index.ts:453-464 (schema)

  Defines the input schema and metadata for the MCP tool, specifying that it requires an 'emailId' string parameter.

  name: 'get_email_attachments',
  description: 'Get list of attachments for an email',
  inputSchema: {
    type: 'object',
    properties: {
      emailId: {
        type: 'string',
        description: 'ID of the email',
      },
    },
    required: ['emailId'],
  },

• src/index.ts:970-985 (registration)

  MCP server request handler case that dispatches the tool call, validates input, invokes the JmapClient handler, and formats the response.

  case 'get_email_attachments': {
    const { emailId } = args as any;
    if (!emailId) {
      throw new McpError(ErrorCode.InvalidParams, 'emailId is required');
    }
    const client = initializeClient();
    const attachments = await client.getEmailAttachments(emailId);
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(attachments, null, 2),
        },
      ],
    };
  }

• src/index.ts:452-465 (registration)

  Tool registration entry in the MCP server's tools list, including name, description, and schema.

  {
    name: 'get_email_attachments',
    description: 'Get list of attachments for an email',
    inputSchema: {
      type: 'object',
      properties: {
        emailId: {
          type: 'string',
          description: 'ID of the email',
        },
      },
      required: ['emailId'],
    },
  },