MCP and AI basics
Resource
Read-only data an MCP server hands to the assistant as context, such as a document, a database schema or a file. Unlike a tool, a resource does not perform an action.
A resource is data an MCP server hands to the assistant as context rather than as the result of an action. A product feed, a policy document, a database schema or a saved report can all be resources. Each has an address (a URI) and a content type, and the assistant or the user chooses when to load it.
The difference from a tool is intent. Calling a tool does something and may have side effects; reading a resource only supplies information. For a merchant this is the safer of the two, and it is a natural fit for reference material you want every conversation to start from, such as your shipping and returns rules.
Not every host supports resources equally well, and many e-commerce servers expose tools only. When a server lists resources, check how large they are: a resource that pulls an entire catalog into the conversation will consume the context window quickly and can make answers worse rather than better.