cxxmcp

A production-ready C++17 SDK for the Model Context Protocol — build MCP servers and clients that embed directly into native C++ applications, with full protocol coverage and cross-SDK conformance validation.

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Quick Start

find_package(cxxmcp CONFIG REQUIRED)
target_link_libraries(my_server PRIVATE cxxmcp::server)
target_link_libraries(my_client PRIVATE cxxmcp::client)

#include <cxxmcp/peer.hpp>
#include <cxxmcp/run.hpp>

int main() {
    return mcp::ServerPeer::builder()
        .name("demo-server")
        .version("1.0.0")
        .stdio()
        .tool<mcp::protocol::Json, mcp::protocol::Json>("echo",
            [](const mcp::protocol::Json& input) {
                return mcp::protocol::Json{{"echo", input}};
            })
        .run();
}

// Client side
#include <cxxmcp/peer.hpp>
#include <cxxmcp/run.hpp>

int main() {
    int status = 0;
    const auto run_status = mcp::ClientPeer::builder()
        .streamable_http("http://127.0.0.1:3000/mcp")
        .run([&status](https://github.com/caomengxuan666/cxxmcp/blob/master/auto&) {
            if (!svc.peer().initialize().has_value() ||
                !svc.peer().notify_initialized().has_value() ||
                !svc.peer().list_all_tools().has_value() ||
                !svc.peer()
                     .call_tool("echo",
                                mcp::protocol::Json{{"value", "hello"}})
                     .has_value()) {
                status = 1;
            }
        });
    return run_status == 0 ? status : run_status;
}

What It Covers

Protocol coverage: tool, prompt, resource, resource template, completion, logging, roots, sampling, elicitation, task lifecycle, progress, cancellation, and raw JSON-RPC escape hatches for vendor extensions.

Conformance: Validated against the official modelcontextprotocol/conformance runner (--suite all).

Full details in conformance evidence.

Capability Snapshot

cxxmcp is a release-candidate-quality C++ MCP SDK with full protocol coverage, cross-SDK conformance validation, and multiple transport options. See conformance evidence and ecosystem maturity evidence for details.

Install

find_package(cxxmcp CONFIG REQUIRED)

# Server
target_link_libraries(my_server PRIVATE cxxmcp::server)
# Client
target_link_libraries(my_client PRIVATE cxxmcp::client)
# Everything
target_link_libraries(my_app PRIVATE cxxmcp::sdk)

Build from source:

cmake -S . -B build -DCXXMCP_BUILD_CLIENT=ON -DCXXMCP_BUILD_SERVER=ON
cmake --build build --config Release
cmake --install build --config Release --prefix out/install/cxxmcp

The quick-start client uses Streamable HTTP, so source builds that compile that client path must also set -DCXXMCP_ENABLE_HTTP=ON.

Package managers: conanfile.py (Conan 2), packaging/vcpkg/ports/cxxmcp-sdk (vcpkg overlay), packaging/xmake/ (xmake). See package consumption.

CMake Options

Package Targets

Why cxxmcp

• Standard CMake SDK consumption — find_package and go
• C++17 public API, no runtime dependencies beyond the standard library
• Full MCP protocol coverage with typed, capability-gated helpers
• Cross-SDK conformance validation against the official runner
• RMCP-style Peer/Service architecture designed for embedding
• stdio, process-stdio, Streamable HTTP, and WebSocket transports out of the box

Examples

In-tree examples cover server/client peers, auth, tasks, elicitation, and transport adapters. Run them with:

cmake --preset examples && cmake --build --preset examples && ctest --preset examples

See examples.md for the full list. The separate cxxmcp-examples repository exercises the SDK through an external CMake project with advanced scenarios.

Documentation

• GitHub Pages — API reference
• Conformance evidence — test results and known exceptions
• Compatibility policy — versioning, compiler matrix, ABI
• Dependency policy — update policy and package dependency boundaries
• HTTP transport backend evidence
• Release gates — release-blocking checks
• Runtime gateway — external gateway boundary
• Examples — full example list
• Auth design — OAuth 2.1 / DPoP direction
• Request lifecycle — timeout, cancellation, progress, shutdown
• Contributing | Security | Changelog

Status

cxxmcp is a community C++ MCP SDK preparing official SDK candidate evidence. The Peer/Service boundary, transport layer, and conformance gates are in release-candidate shape. It is not an official MCP SDK unless accepted by the MCP maintainers.

Compiler Compatibility

MinGW UCRT64 GCC and MinGW CLANG64 Clang are tracked as provisional, best-effort compiler compatibility evidence. These targets are not release-supported. The compiler-compat workflow runs them with continue-on-error: true while they remain provisional.