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Model Context Protocol (MCP)

The Model Context Protocol (MCP) is a standardized protocol that enables AI models to interact with external tools and resources in a structured way. It supports multiple transport mechanisms to provide flexibility across different environments.

The MCP Java SDK provides a Java implementation of the Model Context Protocol, enabling standardized interaction with AI models and tools through both synchronous and asynchronous communication patterns.

Spring AI MCP extends the MCP Java SDK with Spring Boot integration, providing both client and server starters. Bootstrap your AI applications with MCP support using Spring Initializer.

MCP Java SDK Architecture

This section provides an overview for the MCP Java SDK architecture. For the Spring AI MCP integration, refer to the Spring AI MCP Boot Starters documentation.

The Java MCP implementation follows a three-layer architecture:

MCP Stack Architecture

  • Client/Server Layer: The McpClient handles client-side operations while the McpServer manages server-side protocol operations. Both utilize McpSession for communication management.

  • Session Layer (McpSession): Manages communication patterns and state through the McpClientSession and McpServerSession implementations.

  • Transport Layer (McpTransport): Handles JSON-RPC message serialization and deserialization with support for multiple transport implementations.
MCP Client

The MCP Client is a key component in the Model Context Protocol (MCP) architecture, responsible for establishing and managing connections with MCP servers. It implements the client-side of the protocol, handling:

  • Protocol version negotiation to ensure compatibility with servers

  • Capability negotiation to determine available features

  • Message transport and JSON-RPC communication

  • Tool discovery and execution

  • Resource access and management

  • Prompt system interactions

  • Optional features:

    • Roots management

    • Sampling support

  • Synchronous and asynchronous operations

  • Transport options:

    • Stdio-based transport for process-based communication

    • Java HttpClient-based SSE client transport

    • WebFlux SSE client transport for reactive HTTP streaming
Java MCP Client Architecture
MCP Server

The MCP Server is a foundational component in the Model Context Protocol (MCP) architecture that provides tools, resources, and capabilities to clients. It implements the server-side of the protocol, responsible for:

  • Server-side protocol operations implementation

    • Tool exposure and discovery

    • Resource management with URI-based access

    • Prompt template provision and handling

    • Capability negotiation with clients

    • Structured logging and notifications

  • Concurrent client connection management

  • Synchronous and Asynchronous API support

  • Transport implementations:

    • Stdio-based transport for process-based communication

    • Servlet-based SSE and Streamable-HTTP server transports

    • WebFlux SSE and Streamable-HTTP server transports for reactive HTTP streaming

    • WebMVC SSE and Streamable-HTTP server transports for servlet-based HTTP streaming
Java MCP Server Architecture

For detailed implementation guidance, using the low-level MCP Client/Server APIs, refer to the MCP Java SDK documentation. For simplified setup using Spring Boot, use the MCP Boot Starters described below.

Spring AI MCP Integration

Spring AI provides MCP integration through the following Spring Boot starters:

Client Starters

  • spring-ai-starter-mcp-client - Core starter providing STDIO and HTTP-based SSE and Streamable-HTTP support

  • spring-ai-starter-mcp-client-webflux - WebFlux-based SSE and Streamable-HTTP transport implementation

Server Starters

STDIO

Server Type Dependency Property

Standard Input/Output (STDIO)

spring-ai-starter-mcp-server

spring.ai.mcp.server.stdio=true

WebMVC

Server Type

Dependency

Property

SSE WebMVC

spring-ai-starter-mcp-server-webmvc

spring.ai.mcp.server.protocol=SSE or empty

Streamable-HTTP WebMVC

spring-ai-starter-mcp-server-webmvc

spring.ai.mcp.server.protocol=STREAMABLE

Stateless WebMVC

spring-ai-starter-mcp-server-webmvc

spring.ai.mcp.server.protocol=STATLESS

WebMVC (Reactive)

Server Type

Dependency

Property

SSE WebFlux

spring-ai-starter-mcp-server-webflux

spring.ai.mcp.server.protocol=SSE or empty

Streamable-HTTP WebFlux

spring-ai-starter-mcp-server-webflux

spring.ai.mcp.server.protocol=STREAMABLE

Stateless WebFlux

spring-ai-starter-mcp-server-webflux

spring.ai.mcp.server.protocol=STATLESS

Spring AI MCP Annotations

In addition to the programmatic MCP client & server configuration, Spring AI provides annotation-based method handling for MCP servers and clients through the MCP Annotations module. This approach simplifies the creation and registration of MCP operations using a clean, declarative programming model with Java annotations.

The MCP Annotations module enables developers to:

  • Create MCP tools, resources, and prompts using simple annotations

  • Handle client-side notifications and requests declaratively

  • Reduce boilerplate code and improve maintainability

  • Automatically generate JSON schemas for tool parameters

  • Access special parameters and context information

Key features include:

  • Server Annotations: @McpTool, @McpResource, @McpPrompt, @McpComplete

  • Client Annotations: @McpLogging, @McpSampling, @McpElicitation, @McpProgress

  • Special Parameters: McpSyncServerExchange, McpAsyncServerExchange, McpTransportContext, McpMeta

  • Automatic Discovery: Annotation scanning with configurable package inclusion/exclusion

  • Spring Boot Integration: Seamless integration with MCP Boot Starters

Additional Resources