Interop — MCP · A2A · AG-UI
eidan speaks three open protocols on three boundaries, in and out, so it plugs into an existing stack instead of replacing it.
MCP — tools
The Model Context Protocol is eidan's tool boundary.
- In: the
mcp-serverplugin exposes eidan's own tools to external agents (Claude Code, other MCP clients), served on:8091. - Out: the engine is an MCP client too, so eidan can call tools on external MCP servers — extend its reach without writing a plugin.
A2A — agents
The Agent-to-Agent boundary lets other agents delegate to eidan. The a2a-server plugin
exposes eidan as an A2A agent (on :8095), so a larger multi-agent system can hand it work and
consume its result.
AG-UI — the chat wire
AG-UI is the protocol between the agent and a frontend. It's the wire behind the web chat
(POST /api/turn, served on :8090) — a streaming turn API the reference Next.js app renders. Build
your own frontend against it if you don't want the reference one.
At a glance
| Protocol | Boundary | Direction | Plugin / surface | Port |
|---|---|---|---|---|
| MCP | Tools | in + out | mcp-server (+ engine MCP client) | :8091 |
| A2A | Agents | in | a2a-server | :8095 |
| AG-UI | Frontend | — | frontend-agui (/api/turn) | :8090 |
Because these are open standards, eidan is a citizen of the wider ecosystem rather than a walled garden — the same reasoning behind owning your stack.