agentd-mcp

The Model Context Protocol layer agentd talks to servers through. It wraps the official rmcp SDK in a blocking client, and runs it over a transport you control.

That second half is the reason this crate exists. rmcp owns the protocol — the handshake, the typed requests and notifications, capability negotiation, the version table — and tracking the specification upstream is exactly what you want from a protocol implementation. What its own transport cannot do is carry a credential your deployment requires: an AAuth request signature with its challenge/re-sign loop, an AWS SigV4 signature computed per request, an mTLS client identity, an OAuth token you refresh, an SSRF guard on every dial.

So rmcp_transport implements the SDK's StreamableHttpClient over agentd-net's HTTP stack. The SDK speaks the protocol; you keep the socket.

use agentd_mcp::client::McpClient;
use std::time::Duration;

let mut mcp = McpClient::connect(
    "github",
    "https://mcp-github.internal/mcp",
    vec![],
    Duration::from_secs(30),
)?;
mcp.initialize()?;

for tool in mcp.list_tools()? {
    println!("{}", tool.name);
}
let out = mcp.call_tool("list_issues", None)?;
# Ok::<(), Box<dyn std::error::Error>>(())

What's in it

• A blocking client over the async SDK, so a synchronous runtime does not need an executor of its own.
• Server→client requests answered — ping unconditionally (the spec says both sides MUST), elicitation/create delegated to a host handler that can ask a human, and an undeclared capability refused with -32601 rather than met with silence.
• Notifications reach you — resources/updated and the list-changed family land in a queue you drain, which is what makes a subscribe-and-react daemon possible.
• The version/era model — the legacy and stateless revisions, and which subscription mechanism each defines.
• A JSON-RPC codec and an HTTP server framework, used by agentd's own listeners.

Scope

This is agentd's MCP layer, published because the blocking-client-over-your-own- socket shape is not something you can get from the SDK alone. The API is shaped by what agentd needs and moves with it.

Licensed under Apache-2.0. Source and issues: https://github.com/agentd-dev/source-code.