Not all social media companies are created equal, but a good agency can align your customer-facing channels with your business goals. A good agency will look beyond vanity metrics such as page likes and focus on the things that really matter to your business.
On a more technical, day-to-day basis, a social media company, like Mint, will help you to plan out key activities, produce and post content, manage customer interactions, answer questions and enquiries, increase the reach of content, manage your community, along with other activities. These day-to-day activities would depend heavily on your social media strategy and how your business needs to utilise social channels to support your broader business objectives.