mcp-brokerSAFE

An MCP gateway for tool servers that aren't up yet.

Point your agent at the broker instead of at each tool server. A server that is still booting — or that you haven't started — doesn't block the session and doesn't appear as a phantom tool that hangs on first call. When it comes up, its tools appear mid-session, without restarting the agent or the broker.

It's a library, not a service: you mount it in your own ASGI app.

The problem

Agent runtimes read their MCP server list once, at session start. So every tool server has to be listening before the agent starts, and your startup time is the slowest one. Anything heavy — a browser, a CAD toolchain, a model server — is either on the critical path or missing for the whole session.

Point the agent at a broker instead and that ordering constraint goes away.

Install

pip install mcp-broker

Use

from mcp_broker import ToolBroker, broker_route

broker = ToolBroker.from_env([
("office", "http://127.0.0.1:9101/mcp"),
("slowly", "http://127.0.0.1:9102/mcp"),   # not running yet — fine
])

app = Starlette(lifespan=...)          # see examples/serve_broker.py
for name in broker.names:
app.mount(broker_route(name), broker.asgi_app(name))

broker.run() — an async context manager, entered from your lifespan — owns the dial loop that notices an upstream arriving and pushes tools/list_changed to every attached session. Without it the broker still proxies, but nothing ever appears mid-session.

Each upstream gets its own endpoint, /_broker//mcp, so agents see them as separate servers and can be granted them separately.

Using it from Claude Code

claude mcp add --transport http office http://127.0.0.1:9000/_broker/office/mcp
claude mcp add --transport http slowly http://127.0.0.1:9000/_broker/slowly/mcp

Both register instantly, whether or not the upstream behind them is running.

Any MCP client works the same way — the broker sp