The Model Context Protocol (MCP) defines three core primitives that servers expose to clients, providing a standardized way to share contextual information, tools, and workflows.
Primitives
- Tools: Action-oriented capabilities triggered by the model (e.g., performing computations, retrieving computed results). Defined with JSON schema; model-controlled.
- Resources: Static, read-only data sources addressable by URI (e.g., database records, files). Application-controlled and injected into context.
- Prompts: User-controlled, reusable workflow templates, pre-populated with parameters at selection time.
Key Takeaways
- Tools enable models to interact with the external world (model-controlled).
- Resources expose static data for context (read-only).
- Prompts standardize complex, multi-step workflows.