Hunter.io MCP Server

Instructions

Implementation Reference

• src/index.ts:557-591 (handler)

  The handler for the 'hunter_email_count' tool. Validates input parameters using isEmailCountParams, calls the Hunter.io /email-count API endpoint with retry logic via withRetry, and returns the response or error.

  case 'hunter_email_count': {
    if (!isEmailCountParams(args)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Invalid arguments for hunter_email_count'
      );
    }
  
    try {
      // Hunter.io API expects query parameters for email count
      const response = await withRetry(
        async () => apiClient.get('/email-count', { params: args }),
        'email count'
      );
  
      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify(response.data, null, 2),
          },
        ],
        isError: false,
      };
    } catch (error) {
      const errorMessage = axios.isAxiosError(error)
        ? `API Error: ${error.response?.data?.message || error.message}`
        : `Error: ${error instanceof Error ? error.message : String(error)}`;
  
      return {
        content: [{ type: 'text', text: errorMessage }],
        isError: true,
      };
    }
  }

• src/index.ts:96-113 (schema)

  Tool definition for 'hunter_email_count' including name, description, and input schema (domain or company as optional strings).

  const EMAIL_COUNT_TOOL: Tool = {
    name: 'hunter_email_count',
    description: 'Know how many email addresses we have for a domain or a company.',
    inputSchema: {
      type: 'object',
      properties: {
        domain: {
          type: 'string',
          description: 'The domain name to get the count for, e.g. "stripe.com"',
        },
        company: {
          type: 'string',
          description: 'The company name to get the count for (alternative to domain)',
        }
      },
      required: [],
    },
  };

• src/index.ts:424-432 (registration)

  Registers the 'hunter_email_count' tool (via EMAIL_COUNT_TOOL) in the ListToolsRequest handler response.

    tools: [
      FIND_EMAIL_TOOL,
      VERIFY_EMAIL_TOOL,
      DOMAIN_SEARCH_TOOL,
      EMAIL_COUNT_TOOL,
      ACCOUNT_INFO_TOOL,
    ],
  }));

• src/index.ts:274-308 (helper)

  Type guard function that validates the input arguments for the 'hunter_email_count' tool, ensuring it's an object with at least one of 'domain' or 'company' as strings.

  function isEmailCountParams(args: unknown): args is EmailCountParams {
    if (
      typeof args !== 'object' ||
      args === null
    ) {
      return false;
    }
  
    // At least one of domain or company must be provided
    if (
      !('domain' in args || 'company' in args)
    ) {
      return false;
    }
  
    // Check domain if provided
    if (
      'domain' in args &&
      (args as { domain: unknown }).domain !== undefined &&
      typeof (args as { domain: unknown }).domain !== 'string'
    ) {
      return false;
    }
  
    // Check company if provided
    if (
      'company' in args &&
      (args as { company: unknown }).company !== undefined &&
      typeof (args as { company: unknown }).company !== 'string'
    ) {
      return false;
    }
  
    return true;
  }

• src/index.ts:146-149 (schema)

  TypeScript interface defining the parameter shape for 'hunter_email_count' tool.

  interface EmailCountParams {
    domain?: string;
    company?: string;
  }