Building an AI Chat Agent with MCP, Spring AI

Model Context Protocol (MCP) is an open standard for connecting AI apps to tools and data sources. A useful way to think about it is as a USB-C port for AI: one standard interface that lets different models plug into different capabilities without custom glue code for every integration. In this project, we combine MCP, Spring AI, and Google Gemini to build a chat app that can answer weather questions using real tools instead of hallucinating. The system has three parts: MCP tool server - a Spring Boot service that exposes weather and geocoding tools AI chat agent - a Spring Boot service that uses Spring AI + Gemini and calls MCP tools when needed React chat UI - a lightweight frontend for sending messages and rendering replies The result is a small but realistic architecture you can extend into a production assistant. Architecture User (Browser:3000) | POST /api/chat v AI Agent (Spring:7171) -- MCP / Streamable HTTP --> MCP Server (Spring:7170) | | | Google Gemini | Bright Sky API (weather) | | OpenStreetMap Nominatim (geocoding) v v Chat response Tool execution The full source code is available on GitHub . 1. The MCP Tool Server The tool server is a Spring Boot application that exposes MCP tools through Spring AI's annotation scanner. It runs on port 7170 and uses Streamable HTTP for transport. Dependencies <dependency> <groupId> org.springframework.ai </groupId> <artifactId> spring-ai-starter-mcp-server-webmvc </artifactId> </dependency> <dependency> <groupId> org.springframework.boot </groupId> <artifactId> spring-boot-starter-web </artifactId> </dependency> Defining tools With Spring AI, a tool is just a Spring bean method annotated with @McpTool : @Component public class WeatherTool { private final WeatherToolService weatherToolService ; public WeatherTool ( WeatherToolService weatherToolService ) { this . weatherToolService = weatherToolService ; } @McpTool ( name = "get_current_weather" , description = "Get current weather by dwd_station_id or by lat/lon" ) p