Crate model_context_protocol 

MCP - Model Context Protocol

A Rust implementation of the Model Context Protocol (MCP) for AI tool integration.

This crate provides the infrastructure for communicating with MCP servers via stdio/HTTP transports.

Features

• McpServer: Core MCP server with tools and capabilities
• McpServerHub: Aggregates multiple external servers into one
• Multiple Transports: Support for stdio and HTTP-based MCP servers
• Tool Routing: Automatic routing of tool calls to the correct server
• Macros: #[mcp_tool] for easy tool definitions from functions

Quick Start - Creating a Server

use mcp::macros::mcp_tool;
use mcp::server::stdio::McpStdioServer;
use mcp::McpServerConfig;

// Define tools as simple functions
#[mcp_tool(description = "Add two numbers")]
fn add(a: f64, b: f64) -> f64 { a + b }

#[mcp_tool(description = "Subtract two numbers")]
fn subtract(a: f64, b: f64) -> f64 { a - b }

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let config = McpServerConfig::builder()
        .name("calculator")
        .version("1.0.0")
        .with_tools(tools![AddTool, SubtractTool])
        .build();

    McpStdioServer::run(config).await?;
    Ok(())
}

Aggregating Multiple Servers

use mcp::{McpServerHub, McpServerConnectionConfig};
use mcp::server::stdio::McpStdioServer;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a hub that aggregates external servers
    let hub = std::sync::Arc::new(McpServerHub::new("aggregator", "1.0.0"));

    // Connect to external servers
    hub.connect(McpServerConnectionConfig::stdio("calc", "node", vec!["calc.js".into()])).await?;
    hub.connect(McpServerConnectionConfig::stdio("files", "python", vec!["files.py".into()])).await?;

    // Wrap as a stdio server - all tools are now exposed
    McpStdioServer::run(hub.to_config()).await?;
    Ok(())
}

Feature Flags

• default - Enables stdio, http, and macros features
• client - Client transports for connecting to external MCP servers
• stdio-server - Stdio server transport
• http-server - HTTP server with actix-web
• macros - Procedural macros for defining tools

Re-exports

pub use protocol::CallToolParams;

pub use protocol::CallToolResult;

pub use protocol::ClientInbound;

pub use protocol::JsonRpcError;

pub use protocol::JsonRpcId;

pub use protocol::JsonRpcMessage;

pub use protocol::JsonRpcNotification;

pub use protocol::JsonRpcPayload;

pub use protocol::JsonRpcRequest;

pub use protocol::JsonRpcResponse;

pub use protocol::ListToolsParams;

pub use protocol::ListToolsResult;

pub use protocol::McpCapabilities;

pub use protocol::McpServerInfo;

pub use protocol::McpToolDefinition;

pub use protocol::ServerOutbound;

pub use protocol::ToolContent;

pub use protocol::ToolInputSchema;

pub use protocol::Annotations;

pub use protocol::BaseMetadata;

pub use protocol::BooleanSchema;

pub use protocol::CancelTaskParams;

pub use protocol::CompleteArgument;

pub use protocol::CompleteContext;

pub use protocol::CompleteParams;

pub use protocol::CompleteResult;

pub use protocol::CompletionData;

pub use protocol::CreateMessageParams;

pub use protocol::CreateMessageResult;

pub use protocol::CreateTaskResult;

pub use protocol::ElicitAction;

pub use protocol::ElicitRequestFormParams;

pub use protocol::ElicitRequestParams;

pub use protocol::ElicitRequestUrlParams;

pub use protocol::ElicitResult;

pub use protocol::ElicitationCompleteParams;

pub use protocol::GetTaskParams;

pub use protocol::GetTaskPayloadParams;

pub use protocol::Icon;

pub use protocol::IconTheme;

pub use protocol::Implementation;

pub use protocol::ListRootsResult;

pub use protocol::ListTasksParams;

pub use protocol::ListTasksResult;

pub use protocol::LoggingLevel;

pub use protocol::LoggingMessageParams;

pub use protocol::ModelHint;

pub use protocol::ModelPreferences;

pub use protocol::NumberSchema;

pub use protocol::ProgressNotificationParams;

pub use protocol::ProgressToken;

pub use protocol::PromptReference;

pub use protocol::RelatedTaskMetadata;

pub use protocol::ResourceTemplateReference;

pub use protocol::Role;

pub use protocol::Root;

pub use protocol::SamplingContent;

pub use protocol::SamplingMessage;

pub use protocol::SetLevelParams;

pub use protocol::StringSchema;

pub use protocol::StringSchemaFormat;

pub use protocol::Task;

pub use protocol::TaskMetadata;

pub use protocol::TaskStatus;

pub use protocol::TaskStatusNotificationParams;

pub use protocol::TaskSupport;

pub use protocol::ToolAnnotations;

pub use protocol::ToolChoice;

pub use protocol::ToolChoiceMode;

pub use protocol::ToolExecution;

pub use protocol::ToolResultContent;

pub use protocol::ToolUseContent;

pub use transport::ClientInfo;

pub use transport::InitializeCapabilities;

pub use transport::InitializeParams;

pub use transport::InitializeResult;

pub use transport::McpServerConnectionConfig;

pub use transport::McpTransport;

pub use transport::McpTransportError;

pub use transport::RestartPolicy;

pub use transport::ServerCapabilities;

pub use transport::ServerInfo;

pub use transport::TransportTypeId;

pub use transport::ElicitationCapabilities;

pub use transport::PromptsCapabilities;

pub use transport::ResourcesCapabilities;

pub use transport::RootsCapabilities;

pub use transport::SamplingCapabilities;

pub use transport::ServerToolCapabilities;

pub use transport::TasksCapabilities;

pub use transport::ToolCapabilities;

pub use result::error_result;

pub use result::success_result;

pub use result::tool_err;

pub use result::tool_ok;

pub use result::IntoCallToolResult;

pub use result::ToolResult;

pub use tool::all_tools;

pub use tool::tools_in_group;

pub use tool::BoxFuture;

pub use tool::DynTool;

pub use tool::FnTool;

pub use tool::McpTool;

pub use tool::ToolCallResult;

pub use tool::ToolEntry;

pub use tool::ToolFactory;

pub use tool::ToolProvider;

pub use tool::ToolRegistry;

pub use server::McpServer;

pub use server::McpServerChannels;

pub use server::McpServerConfig;

pub use server::McpServerConfigBuilder;

pub use server::ServerError;

pub use server::ServerStatus;

pub use server::stdio::McpStdioServer;stdio-server

pub use server::http::McpHttpServer;http-server

pub use hub::McpHub;

pub use server_hub::McpServerHub;

pub use client::stdio::AsyncStdioTransport;client

pub use client::stdio::StdioTransportAdapter;client

pub use client::stdio::TokioStdioTransport;client

pub use client::http::HttpTransport;client

pub use client::http::HttpTransportAdapter;client

pub use macro_adapter::MacroServer;macros

pub use macro_adapter::MacroServerAdapter;macros

Modules

circuit_breaker

Circuit breaker pattern for resilient server connections.

clientclient

MCP Client transports for connecting to external MCP servers.

hub

McpHub - Central hub for MCP tool routing across multiple servers.

hub_common

Common hub infrastructure shared between McpHub and McpServerHub.

macro_adaptermacros

Adapter for macro-generated MCP servers.

macrosmacros

Procedural macros for defining MCP servers and tools.

protocol

MCP JSON-RPC Protocol Types

result

Result types for MCP tool implementations.

server

MCP Server with bidirectional async communication.

server_hub

McpServerHub - A hub that aggregates multiple MCP servers into a single server.

tool

Tool traits and types for MCP servers.

transport

McpTransport - Abstract transport interface for MCP servers.

transport_factory

Transport factory for creating MCP transports from configuration.

Macros

fn_tool

Helper macro for creating tools from async functions.

tools

Creates a vector of tools from tool types.

Constants

MCP_PROTOCOL_VERSION

Current MCP protocol version (2025-11-25).

VERSION

Crate version.