MCP Server

The langchain4j-cdi-mcp module tree turns CDI beans into a Model Context Protocol (MCP) server. It exposes annotated bean methods as MCP tools, prompts, and resources over JSON-RPC 2.0 / Streamable HTTP at the /mcp endpoint.

Built on the MCP Java project (java-mcp-annotations).

Quick Setup

Add the MCP server dependency:

<dependency>
    <groupId>dev.langchain4j.cdi.mcp</groupId>
    <artifactId>langchain4j-cdi-mcp-server</artifactId>
    <version>${langchain4j-cdi-mcp.version}</version>
</dependency>

And the appropriate CDI extension for your runtime:

Quarkus / Helidon:

<dependency>
    <groupId>dev.langchain4j.cdi.mcp</groupId>
    <artifactId>langchain4j-cdi-mcp-build-compatible-ext</artifactId>
    <version>${langchain4j-cdi-mcp.version}</version>
</dependency>

WildFly / GlassFish / Liberty:

<dependency>
    <groupId>dev.langchain4j.cdi.mcp</groupId>
    <artifactId>langchain4j-cdi-mcp-portable-ext</artifactId>
    <version>${langchain4j-cdi-mcp.version}</version>
</dependency>

Defining Tools

@ApplicationScoped
public class WeatherService {

    @Tool("Get current weather for a city")
    public String getWeather(
            @ToolArg(description = "City name") String city) {
        return "Sunny, 25C in " + city;
    }
}

Defining Prompts

@ApplicationScoped
public class PromptLibrary {

    @Prompt("Generate a summary prompt")
    public String summarize(
            @PromptArg(description = "Text to summarize") String text) {
        return "Please summarize the following text:\n\n" + text;
    }
}

Defining Resources

@ApplicationScoped
public class DataResources {

    @Resource(uri = "data://config", description = "Application configuration")
    public String getConfig() {
        return loadConfiguration();
    }
}

MCP Capabilities

The MCP server supports these capabilities via framework types injected at invocation time:

Type	Description
McpLog	Structured logging within tool execution
Progress	Report progress to the client
Cancellation	Check if the client cancelled the request
McpConnection	Access to the MCP session
Roots	Access client-provided root URIs
Sampling	Request LLM sampling from the client
Elicitation	Request user input from the client

These parameters are excluded from the generated JSON Schema.

Architecture

• McpEndpoint -- JAX-RS /mcp resource handling JSON-RPC requests
• McpSessionManager -- Session lifecycle with 30-minute default expiry
• McpNotificationBroadcaster -- SSE notifications to connected clients
• JsonSchemaGenerator -- Automatic JSON Schema generation from Java method signatures