Rust SDK for MCP servers and clients

This SDK fully implements the MCP 2026-07-28 stateless protocol and passes 100% of official MCP conformance tests (110/110 server, 440/440 client).

rust-mcp-sdk provides the necessary components for developing both servers and clients in the MCP ecosystem. It leverages the rust-mcp-schema crate for type-safe schema objects and includes powerful procedural macros.

Focus on your application logic, rust-mcp-sdk handles the protocol, transports, and the rest.

⚠️ Version notice: This is rust-mcp-sdk 2.x, implementing the new MCP 2026-07-28 (stateless) specification. For the previous MCP 2025-11-25 specification, use rust-mcp-sdk 1.x:

rust-mcp-sdk = "1"

See the upgrade guide to migrate from 1.x to 2.0.

Version matrix:

SDK version	Protocol	Branch
2.0	MCP 2026-07-28 (stateless)	main
1.x (LTS)	MCP 2025-11-25	release-1.x

Upgrading? See the upgrade guide.

Key Features

• MCP 2026-07-28 (stateless protocol)
• 100% MCP Conformance - server 110/110, client 440/440 on 2026-07-28
• Transports: Stdio, Streamable HTTP, and backward-compatible SSE support
• Framework Agnostic: Axum, Actix, and BYO Server integrations
• MRTR (Mid-Request Turn-Around) for server→client input requests
• Response cache (SEP-2549) with principal-scoped privacy + auto-pagination
• Per-request _meta with RequestContext
• Multi-client concurrency
• DNS Rebinding Protection
• Message Observer (Telemetry & Monitoring)
• HTTP Health Checks (for load balancers & container orchestration)
• OAuth Authentication for MCP Servers
  • Remote Oauth Provider
    • Keycloak Provider (via rust-mcp-extra)
    • WorkOS Authkit Provider (via rust-mcp-extra)
    • Scalekit Authkit Provider (via rust-mcp-extra)
• OAuth Authentication for MCP Clients (metadata discovery, CIMD, PKCE, token refresh, pluggable storage)
• Issuer-bound credentials (SEP-2352), strict iss validation (SEP-2468)

Table of Contents

• Quick Start
• Minimal MCP Server (Stdio)
• Minimal MCP Server (Streamable HTTP)
• Minimal MCP Client (Stdio)
• Usage Examples
• Macros
  • mcp_tool
  • tool_box
  • mcp_elicit
  • mcp_resource
  • mcp_resource_template
  • mcp_prompt
  • mcp_icon
• Authentication
• HTTP Server Backends (Axum & Actix)
• Cargo features
• Handler Traits
• Message Observer (Telemetry & Monitoring)
• Health Check Endpoint
• Projects using Rust MCP SDK
• Contributing
• Development
• License

Quick Start

Add to your Cargo.toml:

[dependencies]
rust-mcp-sdk = "2.0.0"  # Check crates.io for the latest version

Minimal MCP Server (Stdio)

use async_trait::async_trait;
use rust_mcp_sdk::{
    error::SdkResult, macros, mcp_icon,
    mcp_server::{server_runtime, McpServerOptions, ServerHandler},
    schema::*,
    McpServer, RequestContext, ServerDetails, StdioTransport, ToMcpServerHandler,
    TransportOptions,
};

// Define an MCP tool
#[macros::mcp_tool(name = "say_hello", description = "returns \"Hello from Rust MCP SDK!\" message")]
#[derive(Debug, ::serde::Deserialize, ::serde::Serialize, macros::JsonSchema)]
pub struct SayHelloTool {}

// Define a custom handler
#[derive(Default)]
struct HelloHandler;

#[async_trait]
impl ServerHandler for HelloHandler {
    async fn handle_list_tools_request(
        &self,
        _request: Option<PaginatedRequestParams>,
        _context: &RequestContext,
        _runtime: std::sync::Arc<dyn McpServer>,
    ) -> std::result::Result<ListToolsResult, RpcError> {
        Ok(ListToolsResult {
            tools: vec![SayHelloTool::tool()],
            meta: None,
            next_cursor: None,
            cache_scope: Default::default(),
            result_type: "complete".to_string(),
            ttl_ms: 0,
        })
    }

    async fn handle_call_tool_request(
        &self,
        params: CallToolRequestParams,
        _context: &RequestContext,
        _runtime: std::sync::Arc<dyn McpServer>,
    ) -> std::result::Result<ServerResult, CallToolError> {
        if params.name == "say_hello" {
            Ok(ServerResult::CallToolResult(CallToolResult {
                content: vec![ContentBlock::TextContent(TextContent::new(
                    "Hello from Rust MCP SDK!".to_string(),
                    None,
                    None,
                ))],
                is_error: None,
                meta: None,
                result_type: "complete".to_string(),
            }))
        } else {
            Err(CallToolError::unknown_tool(params.name))
        }
    }
}

#[tokio::main]
async fn main() -> SdkResult<()> {
    let server_details = ServerDetails {
        server_info: Implementation {
            name: "hello-rust-mcp".into(),
            version: "0.1.0".into(),
            title: Some("Hello World MCP Server".into()),
            description: Some("A minimal Rust MCP server".into()),
            icons: vec![mcp_icon!(
                src = "https://raw.githubusercontent.com/rust-mcp-stack/rust-mcp-sdk/main/assets/rust-mcp-icon.png",
                mime_type = "image/png",
                sizes = ["128x128"],
                theme = "light"
            )],
            website_url: Some("https://github.com/rust-mcp-stack/rust-mcp-sdk".into()),
        },
        capabilities: ServerCapabilities {
            tools: Some(ServerCapabilitiesTools { list_changed: None }),
            ..Default::default()
        },
        instructions: None,
        meta: None,
    };

    let transport = StdioTransport::new(TransportOptions::default())?;
    let handler = HelloHandler::default().to_mcp_server_handler();
    let server = server_runtime::create_server(McpServerOptions {
        server_details,
        transport,
        handler,
        message_observer: None,
    });
    server.start().await
}

HTTP Server Backends (Axum & Actix)

Creating a Streamable HTTP MCP server in rust-mcp-sdk allows multiple clients to connect simultaneously with no additional setup. The setup is nearly identical to the stdio example , the only difference is which HTTP backend crate you install and which function you call to create the server.

Post only - the 2026-07-28 protocol is stateless. GET and DELETE endpoints return 405 Method Not Allowed.

Axum Backend (rust-mcp-axum)

Add rust-mcp-axum to your dependencies and use create_axum_server() with AxumServerOptions.

use async_trait::async_trait;
use rust_mcp_axum::{create_axum_server, AxumServerOptions};
use rust_mcp_sdk::{
    error::SdkResult, macros,
    mcp_server::ServerHandler, schema::*,
};

// ... (define SayHelloTool and HelloHandler as shown above)

#[tokio::main]
async fn main() -> SdkResult<()> {
    let server_details = ServerDetails { /* ... */ };

    let handler = HelloHandler::default().to_mcp_server_handler();
    let server = create_axum_server(
        server_details,
        handler,
        AxumServerOptions {
            host: "127.0.0.1".to_string(),
            ..Default::default()
        },
    );
    server.start().await?;
    Ok(())
}

Actix-web Backend (rust-mcp-actix)

Add rust-mcp-actix to your dependencies and use create_actix_server() with ActixServerOptions.

use rust_mcp_actix::{create_actix_server, ActixServerOptions};
use rust_mcp_sdk::{
    error::SdkResult,
    mcp_server::ServerHandler, schema::*,
};

// ... (define SayHelloTool and HelloHandler as shown above)

#[tokio::main]
async fn main() -> SdkResult<()> {
    let server_details = ServerDetails { /* ... */ };

    let handler = HelloHandler::default().to_mcp_server_handler();
    let server = create_actix_server(
        server_details,
        handler,
        ActixServerOptions {
            host: "127.0.0.1".to_string(),
            ..Default::default()
        },
    );
    server.start().await?;
    Ok(())
}

BYO-server: Embed MCP in your Existing App

Both backends support a BYO-server (Bring Your Own Server) mode, letting you mount MCP endpoints onto a router or app you already control - no need to hand over the server lifecycle.

Backend	Function	Docs
Axum	mcp_routes(state, &mount_opts, http_handler)	rust-mcp-axum README
Actix-web	mcp_scope(state, http_handler, &mount_opts)	rust-mcp-actix README

Custom HTTP Framework Integrations

The SDK is completely framework-agnostic. If you are using a different HTTP framework (like Rocket, Salvo, or Warp), you can build a custom integration by adapting your framework's native Request/Response types to the SDK's core HTTP handling logic.

See the Custom HTTP Framework Integration Guide for architectural details.

AxumServerOptions

Axum server is highly customizable through AxumServerOptions:

let server = create_axum_server(
    server_details,
    handler.to_mcp_server_handler(),
    AxumServerOptions {
        host: "127.0.0.1".to_string(),
        port: 8080,
        auth: Some(Arc::new(auth_provider)),           // enable authentication
        health_endpoint: Some("/health".into()),         // health check
        sse_support: true,                               // backward-compat SSE
        ..Default::default()
    },
);
server.start().await?;

Security Considerations

• DNS rebinding protection is enabled by default. If allowed_hosts is not set, it auto-derives from host:port.
• When running locally, bind only to localhost (127.0.0.1 / localhost) rather than all network interfaces (0.0.0.0)
• Use TLS/HTTPS for production deployments

Following is implementation of an MCP client that starts the @modelcontextprotocol/server-everything server, discovers the server's capabilities, lists available tools, and calls a tool.

use async_trait::async_trait;
use rust_mcp_sdk::{
    error::SdkResult,
    mcp_client::{client_runtime, ClientHandler, McpClientOptions},
    schema::*,
    ClientDetails, McpClient, StdioTransport, ToMcpClientHandler, TransportOptions,
};

pub struct MyClientHandler;
#[async_trait]
impl ClientHandler for MyClientHandler {
    // Override handler methods as needed.
    // See: crates/rust-mcp-sdk/src/mcp_handlers/mcp_client_handler.rs
}

#[tokio::main]
async fn main() -> SdkResult<()> {
    let client_details = ClientDetails {
        client_info: Implementation {
            name: "simple-rust-mcp-client".into(),
            version: "0.1.0".into(),
            description: None,
            icons: vec![],
            title: None,
            website_url: None,
        },
        capabilities: ClientCapabilities::default(),
    };

    let transport = StdioTransport::create_with_server_launch(
        "npx",
        vec!["-y".to_string(), "@modelcontextprotocol/server-everything@latest".to_string()],
        None,
        TransportOptions::default(),
    )?;

    let handler = MyClientHandler {};
    let client = client_runtime::create_client(McpClientOptions::new(
        client_details,
        transport,
        handler.to_mcp_client_handler(),
    ));
    client.clone().start().await?;

    // Discover the server
    let discover = client.request_discover(Default::default()).await?;
    println!("Supported protocol versions: {:?}", discover.supported_versions);

    // List tools
    let tools = client.request_tool_list(None).await?.tools;
    tools.iter().enumerate().for_each(|(i, tool)| {
        println!("  {}. {} : {}", i + 1, tool.name, tool.description.unwrap_or_default());
    });

    // Call a tool (supports MRTR auto-retry)
    let result = client.call_tool(CallToolRequestParams {
        name: "say_hello".to_string(),
        arguments: None,
        input_responses: None,
        request_state: None,
        meta: RequestMetaObject::default(),
    }).await?;

    client.shut_down().await?;
    Ok(())
}

Usage Examples

For more examples (stdio, Streamable HTTP, clients, auth, etc.), see the examples/ directory.

👉 For step-by-step tutorials (server, client, HTTP deployment, OAuth, and more), see the documentation site.

See the hello-world-mcp-server-stdio example running in the MCP Inspector:

Macros

Enable with the macros feature.

mcp_tool

Generate a Tool from a struct, with metadata (icons, hints, etc.).

#[mcp_tool(
    name = "write_file",
    title = "Write File Tool",
    description = "Create or overwrite a file with new content.",
    destructive_hint = false, idempotent_hint = false, open_world_hint = false, read_only_hint = false,
    meta = r#"{ "key": "value" }"#,
    icons = [(src = "https://website.com/write.png", mime_type = "image/png", sizes = ["128x128"], theme = "light")]
)]
#[derive(rust_mcp_macros::JsonSchema)]
pub struct WriteFileTool {
    /// The target file's path for writing content.
    pub path: String,
    /// The string content to be written to the file
    pub content: String,
}

tool_box!()

Automatically generates an enum based on the provided list of tools.

tool_box!(GreetingTools, [SayHelloTool, SayGoodbyeTool]);
let tools: Vec<Tool> = GreetingTools::tools();

mcp_elicit()

Generates type-safe elicitation (Form or URL mode) for user input.

#[mcp_elicit(message = "Please enter your info", mode = form)]
#[derive(JsonSchema)]
pub struct UserInfo {
    #[json_schema(title = "Name", min_length = 5, max_length = 100)]
    pub name: String,
    #[json_schema(title = "Email", format = "email")]
    pub email: Option<String>,
    #[json_schema(title = "Age", minimum = 15, maximum = 125)]
    pub age: i32,
    #[json_schema(title = "Tags")]
    pub tags: Vec<String>,
}

◾ mcp_resource()

A procedural macro attribute that generates utility methods to create fully populated Resource instances from compile-time metadata , usually used for exposing static assets like files, images, or documents. Also generates a RESOURCE_URI associated constant, usable in match patterns, and a resource_mime_type() accessor.

📝 For complete documentation, example usage, and a list of all available attributes, please refer to https://crates.io/crates/rust-mcp-macros.

◾ mcp_resource_template()

A procedural macro attribute that generates utility methods to create fully populated ResourceTemplate instances from compile-time metadata for exposing parameterized server resources. Also generates a RESOURCE_URI_TEMPLATE associated constant, usable in match patterns, and a resource_template_mime_type() accessor.

📝 For complete documentation, example usage, and a list of all available attributes, please refer to https://crates.io/crates/rust-mcp-macros.

◾ mcp_prompt()

A procedural macro attribute that generates utility methods to create fully populated Prompt instances from compile-time metadata, and , when the optional messages attribute is provided , to parse request arguments (from_arguments) and render them into a GetPromptResult (render). Struct fields become typed prompt arguments (String = required, Option<String> = optional, String + default = fallback), the prompts/get handler itself is left to the user.

📝 For complete documentation, example usage, and a list of all available attributes, please refer to https://crates.io/crates/rust-mcp-macros.

◾ mcp_icon!()

A convenient icon builder for implementations and tools, offering full attribute support including theme, size, mime, and more.

example usage:

let icon: crate::schema::Icon = mcp_icon!(
    src = "http://website.com/icon.png",
    mime_type = "image/png",
    sizes = ["64x64"],
    theme = "dark"
);

Authentication

MCP servers can verify tokens issued by other systems, integrate with external identity providers, or manage the entire authentication process.

RemoteAuthProvider

RemoteAuthProvider enables authentication with identity providers that support Dynamic Client Registration (DCR), letting MCP clients auto-register and obtain credentials.

OAuthProxy

OAuthProxy enables authentication with OAuth providers that don't support DCR.

Cargo Features

Available Features

• server: Activates MCP server capabilities
• client: Activates MCP client capabilities
• macros: Procedural macros for Tool, Elicit, Resource structures
• sse: Server-Sent Events (SSE) transport
• streamable-http: Streamable HTTP transport
• stdio: Standard input/output (stdio) transport
• auth: OAuth authentication support for MCP servers
• tls-no-provider: TLS without a crypto provider

Default Features

All features are enabled by default:

[dependencies]
rust-mcp-sdk = "2.0.0"

Using Only the Server Features

[dependencies]
rust-mcp-sdk = { version = "2.0.0", default-features = false, features = ["server", "macros", "stdio"] }

Using Only the Client Features

[dependencies]
rust-mcp-sdk = { version = "2.0.0", default-features = false, features = ["client", "stdio"] }

Handler Traits

Choosing Between ServerHandler and ServerHandlerCore

• ServerHandler: Recommended. Default implementations for all MCP messages. Override only what you need.
• ServerHandlerCore: Full control over request/notification/error dispatch.

Note: Use server_runtime::create_server() or server_runtime_core::create_server() depending on which handler you implement.

Choosing Between ClientHandler and ClientHandlerCore

Same principles apply on the client side: use client_runtime::create_client() with ClientHandler, or client_runtime_core::create_client() with ClientHandlerCore.

Message Observer (Telemetry & Monitoring)

Implement McpObserver to intercept all incoming and outgoing MCP messages for telemetry, logging, debugging, or monitoring.

let server = server_runtime::create_server(McpServerOptions {
    server_details,
    transport,
    handler: handler.to_mcp_server_handler(),
    message_observer: Some(SimpleServerObserver::new()),
});

Health Check Endpoint

An optional HTTP health check endpoint for load balancers and container orchestration:

let server = create_axum_server(
    server_details,
    handler.to_mcp_server_handler(),
    AxumServerOptions {
        host: "127.0.0.1".into(),
        health_endpoint: Some("/health".into()),
        ..Default::default()
    },
);

Projects using Rust MCP SDK

	Name	Description	Link
	Rust MCP Filesystem	Fast, async MCP server enabling high-performance, modern filesystem operations with advanced features.	GitHub
	MCP Discovery	A lightweight command-line tool for discovering and documenting MCP Server capabilities.	GitHub
	mistral.rs	Blazingly fast LLM inference.	GitHub
	moon	moon is a repository management, organization, orchestration, and notification tool for the web ecosystem, written in Rust.	GitHub
	[destructive_command_guard](https://github.com/Dicklesworthstone/destr