Einstein Bots are the ideal solution for this requirement. They are AI-powered chatbots designed to be deployed on various messaging channels to handle common customer questions and routine tasks automatically. This directly addresses the need for a "messaging tool to address common customer feedback and concerns." By automating these interactions, Einstein Bots deflect simple cases, provide 24/7 support, and free up human agents to focus on more complex issues, thereby extending the support team's capabilities.

A. Slack Connect: This tool is designed for collaboration with external partners and vendors in shared Slack channels, not for handling automated, public-facing customer service inquiries.

B. Service GPT: This is not a specific, standalone product. It refers to the generative AI capabilities (Einstein GPT for Service) that can power tools like bots or assist agents, but it is not the customer-facing messaging tool itself.

1. Salesforce Help, "Einstein Bots": "Einstein Bots are a powerful Service Cloud tool that lets you deliver exceptional customer service. Set up a bot to send messages to customers, answer their questions, and then pass them to an agent if needed. Bots free up your agents’ time so they can concentrate on more complex issues." This directly supports the use of bots for automating common questions and extending agent capabilities.

2. Trailhead, "Einstein Bots Basics" Module, "Get to Know Einstein Bots" Unit: "Einstein Bots automate routine requests and gather information, so your agents can focus on complex issues... Bots can handle the routine work, which frees your agents to handle the more complex issues that require their expertise." This reinforces the bot's role in addressing common issues and extending support capacity.

3. Salesforce Help, "What Is Slack Connect?": "Slack Connect lets you work with people outside your company in channels and direct messages... Replace email and work securely with partners, vendors, or customers in Slack." This confirms Slack Connect's purpose is for direct collaboration, not automated, scalable customer support for common issues.