MCP defines three core primitives that servers can expose:
- Tools: Executable functions that AI applications can invoke to perform actions (e.g., file operations, API calls, database queries)
- Resources: Data sources that provide contextual information to AI applications (e.g., file contents, database records, API responses)
- Prompts: Reusable templates that help structure interactions with language models (e.g., system prompts, few-shot examples)
Each primitive type has associated methods for discovery (*/list), retrieval (*/get), and in some cases, execution (tools/call)
MCP clients will use the */list methods to discover available primitive
As a concrete example, consider an MCP server that provides context about a database. It can expose tools for querying the database, a resource that contains the schema of the database, and a prompt that includes few-shot examples for interacting with the tools.
For more details about server primitives see server concepts.