Documentation
Backends
MCP multiplexing

MCP multiplexing

Federate tools of multiple MCP servers on the agentgateway by using MCP multiplexing.

Before you begin

  1. Install the agentgateway binary.
  2. Install the uv Python package manager.

Configure the agentgateway

  1. Download a multiplex configuration for your agentgateway.

    curl -L https://raw.githubusercontent.com/agentgateway/agentgateway/refs/heads/main/examples/multiplex/config.yaml -o config.yaml

  2. Review the configuration file.

    cat config.yaml
    config.yaml
    binds:
- port: 3000
  listeners:
  - routes:
    - backends:
      - mcp:
          targets:
          - name: time
            stdio:
              cmd: uvx
              args: ["mcp-server-time"]
          - name: everything
            stdio:
              cmd: npx
              args: ["@modelcontextprotocol/server-everything"]
    • Listener: An HTTP listener is configured and bound on port 3000. It includes a basic route that matches all traffic to an MCP backend.
    • Backend: The backend defines two targets: time and everything. Note that the target names cannot include underscores (_). These targets are exposed together a single MCP server to clients.

  3. Optional: To use the agentgateway UI playground later, add the following CORS policy to your config.yaml file. The config automatically reloads when you save the file.

    binds:
- post: 3000
  listeners:
  - routes:
    - policies:
        cors:
          allowOrigins:
            - "*"
          allowHeaders:
            - "*"
      backends:
...

  4. Run the agentgateway.

    agentgateway -f config.yaml

Verify access to tools

  1. Open the agentgateway UI to view your listener and target configuration.

  2. Connect to the MCP test server with the agentgateway UI playground.

    1. From the navigation menu, click Playground.

    2. In the Testing card, review your Connection details and click Connect. The agentgateway UI connects to the targets that you configured and retrieves the tools that are exposed on the targets.

    3. Verify that you see a list of Available Tools. Note that the tools are listed twice, one time with the prefix time and one time with the prefix everything. You now have a federated view of all the tools that are exposed on all defined targets.

  3. Verify access to tools from both targets.

    1. From the Available Tools list, select the everything_echo tool.

    2. In the message field, enter any string, such as hello world, and click Run Tool.

    3. Verify that you see your message echoed in the Response card.

    4. Repeat the steps with the time_get_current_time tool with your timezone, such as America/New_York.

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