Synapse Mcp

Synapse MCP A Modern, High-Performance, Header-Only C++20 SDK for Model Context Protocol

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Synapse MCP is a lightweight, ultra-fast, and deeply integrated C++20 header-only library designed to help developers build Model Context Protocol (MCP) servers and clients with zero friction. Built strictly on modern C++ paradigms, it leverages std::expected and modern standard library features to provide maximum safety without compromising on the bare-metal performance that C++ developers expect.

Why Synapse MCP?

Inspired by the design philosophies of industry standards like spdlog and abseil:

• Header-only: Just drop the include/ folder into your project and you're ready to go. No complex build steps or linking headaches.
• Modern C++20/23: Utilizes the latest language features (std::expected, std::variant, std::optional) for expressive, safe, and clean code.
• Zero Overhead Abstractions: Designed for latency-critical applications where every CPU cycle counts.
• Fully Featured MCP Spec: Supports Tools, Resources, Prompts, and Sampling natively out-of-the-box.
• Multi-Threaded & Thread-Safe: Handles incoming JSON-RPC requests asynchronously via std::thread, using std::shared_mutex to safely protect all state interactions.
• Dependency Light: Uses only nlohmann/json for robust JSON-RPC 2.0 serialization.

Installation

Since Synapse MCP is header-only, installation is trivial.

Option 1: CMake FetchContent (Recommended)

Add this to your CMakeLists.txt:

include(FetchContent)
FetchContent_Declare(
    synapse_mcp
    GIT_REPOSITORY https://github.com/ptai-eng/synapse-mcp.git
    GIT_TAG main
)
FetchContent_MakeAvailable(synapse_mcp)

add_executable(my_server main.cpp)
target_link_libraries(my_server PRIVATE synapse::mcp)

Option 2: Copy-Paste

1. Copy the include/synapse directory into your project's include path.
2. Ensure you have nlohmann/json available in your project.

Quick Start

Building an MCP server in modern C++ is now just a few lines of code:

#include 
#include 

int main() {
    // 1. Initialize the STDIO transport layer
    auto transport = std::make_shared();
    
    // 2. Create the MCP Server instance
    synapse::server mcp_server(transport);
    
    // 3. Register a tool
    mcp_server.register_tool(
        "calculate_hash",
        "Computes a dummy SHA-256 hash for a given input string.",
        R"({
            "type": "object",
            "properties": {
                "input": { "type": "string" }
            },
            "required": ["input"]
        })"_json,
        [](const nlohmann::json& args) -> std::expected {
            std::string input = args["input"];
            return nlohmann::json{{"hash", "dummy-hash-" + input}};
        }
    );
    
    // 4. Start listening for incoming requests
    transport->start();
    
    return 0;
}

Documentation

Detailed documentation on handling Prompts, Resources, and advanced Transport layers (like SSE or WebSockets) is coming soon in the docs/ folder.

Contributing

We welcome contributions! Whether it's adding new transport layers, improving documentation, or fixing bugs, please feel free to open an issue or submit a Pull Request.

License

Synapse MCP is distributed under the MIT License. See LICENSE for more information.

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: ptai-eng
• Source: ptai-eng/synapse-mcp
• License: MIT

Install and usage instructions live in the source repository linked above.