mcp-stdio-rs

Minimal embeddable Rust MCP stdio client for MNEMOS and compatible servers.

Quick start

For the current alpha, add it from a Git dependency:

[dependencies]
mcp-stdio-rs = { git = "https://example.com/your-org/mcp-stdio-rs", version = "0.1.0" }

Or, once published:

cargo add mcp-stdio-rs

Public API summary

• McpStdioClient::spawn(cmd, args, env) starts an MCP server process over stdio and completes the initialize handshake.
• client.list_tools() returns the server's available ToolDef values.
• client.call_tool(name, args) sends tools/call with JSON arguments and returns ToolResult.
• client.shutdown() sends a best-effort shutdown, kills the child process if needed, and joins the stdout reader task.

Example

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let c = mcp_stdio_rs::McpStdioClient::spawn("ssh", &["ultra", "mnemos-mcp"], &[]).await?;
    let r = c.call_tool("search_memories", serde_json::json!({ "query": "release notes" })).await?;
    println!("{r:#?}");
    c.shutdown().await?;
    Ok(())
}

Why not tonic+gRPC

MCP over stdio is process-spawned newline-delimited JSON-RPC: one JSON object per line on the server child's stdin/stdout. It does not require HTTP/2, protobuf schemas, a gRPC server, or a generated tonic client.

Compatibility

• Rust 1.86+
• MCP protocol version 2024-11-05
• Pure Rust client code with no Python runtime linkage