Learn MCP By Building

The “Learn MCP By Building” server is a hands‑on reference implementation of the Model Context Protocol (MCP). It demonstrates how to expose a set of tools—such as a simple calculator—to an AI assistant while handling the full MCP lifecycle: protocol initialization, capability negotiation, tool registration, and JSON‑RPC 2.0 messaging over multiple transports (STDIO and HTTP+SSE). By providing a clean, modular architecture, the server solves the problem of connecting AI assistants to external functionality without requiring bespoke integrations for each tool or data source.

At its core, the server implements JSON‑RPC 2.0 as defined by MCP, ensuring that every request and response follows a consistent format. It also supports the standard MCP error schema, giving clients clear, machine‑readable feedback when a tool invocation fails or parameters are invalid. The calculator example illustrates how tools can be defined with JSON Schema, enabling automatic validation and introspection. Developers can see the tool’s capabilities—add, subtract, multiply, divide—alongside required parameters and error conditions, all of which are discoverable by an AI assistant during capability negotiation.

The server’s transport layer is a standout feature. It ships with both STDIO and HTTP+SSE support, allowing developers to choose the most appropriate channel for their environment. The HTTP+SSE transport is particularly valuable in browser‑based workflows, as it exposes a lightweight web interface that lets users interact with the server in real time. The included “MCP Inspector” integration further simplifies debugging, providing a visual dashboard that displays incoming requests, outgoing responses, and the current tool registry.

Real‑world use cases for this server include building a “calculator” skill into a chatbot, creating a data‑retrieval tool that queries an internal database, or exposing a set of microservices as MCP tools for a multimodal assistant. Because the server follows the official MCP spec, any AI client that understands the protocol can seamlessly discover and invoke these tools, making it a drop‑in solution for rapid prototyping or production deployments.

In summary, “Learn MCP By Building” offers a fully functional, transport‑agnostic MCP server that demonstrates best practices for tool registration, validation, and error handling. It equips developers with a clear blueprint for integrating external capabilities into AI assistants, while the included web client and inspector tools make experimentation and debugging straightforward.