Dynamic MCP

Route to a Model Context Protocol (MCP) server dynamically by using a label selector. This way, unlike a static backend, you can update the backing MCP server without having to update the Backend resource. For more information, see the About MCP topic.

⚠️

Note that only streamable HTTP is currently supported for label selectors. If you need to use an SSE listener, use a static MCP Backend.

Before you begin

Set up an agentgateway proxy.

Step 1: Deploy an MCP server

Deploy an MCP server that you want agentgateway to proxy traffic to. The following example sets up an MCP server that provides various utility tools.

Create an MCP server (mcp-server) that provides various utility tools. Notice the following details about the Service:

appProtocol: kgateway.dev/mcp (required): Configure your service to use the MCP protocol. This way, the agentgateway proxy uses the MCP protocol when connecting to the service.
kgateway.dev/mcp-path annotation (optional): The default values are /sse for the SSE protocol or /mcp for the Streamable HTTP protocol. If you need to change the path of the MCP target endpoint, set this annotation on the Service.

kubectl apply -f- <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mcp-server-everything
  labels:
    app: mcp-server-everything
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mcp-server-everything
  template:
    metadata:
      labels:
        app: mcp-server-everything
    spec:
      containers:
        - name: mcp-server-everything
          image: node:20-alpine
          command: ["npx"]
          args: ["-y", "@modelcontextprotocol/server-everything", "streamableHttp"]
          ports:
            - containerPort: 3001
---
apiVersion: v1
kind: Service
metadata:
  name: mcp-server-everything
  labels:
    app: mcp-server-everything
spec:
  selector:
    app: mcp-server-everything
  ports:
    - protocol: TCP
      port: 3001
      targetPort: 3001
      appProtocol: kgateway.dev/mcp
  type: ClusterIP
EOF

Create a Backend for your MCP server that uses label selectors to select the MCP server.
```
kubectl apply -f- <<EOF
apiVersion: gateway.kgateway.dev/v1alpha1
kind: Backend
metadata:
  name: mcp-backend
spec:
  mcp:
    targets:
      - name: mcp-server-everything
        selector:
          services:
            matchLabels:
              app: mcp-server-everything
EOF
```
ℹ️

Plan to attach policies to your selector-based Backend later? You can still attach the policy to a particular backing Service. To do so, set the targetRef setting in the policy to the backing Service, not to the Backend’s service selector. Include the sectionName of the port that you want the policy to apply to. For an example, check out the BackendTLSPolicy guide.

Step 2: Route with agentgateway

Create an HTTPRoute resource that routes to the Backend that you created in the previous step.

kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: mcp
  labels:
    example: mcp-route
spec:
  parentRefs:
    - name: agentgateway
      namespace: kgateway-system
  rules:
    - backendRefs:
        - name: mcp-backend
          group: gateway.kgateway.dev
          kind: Backend
EOF

Step 3: Verify the connection

Use the MCP Inspector tool to verify that you can connect to your MCP server through agentgateway.

Get the agentgateway address.

export INGRESS_GW_ADDRESS=$(kubectl get gateway agentgateway -n kgateway-system -o=jsonpath="{.status.addresses[0].value}")
echo $INGRESS_GW_ADDRESS

kubectl port-forward deployment/agentgateway -n kgateway-system 8080:80

From the terminal, install the MCP Inspector tool. Then, the MCP Inspector opens in your browser. If the MCP inspector tool does not open automatically, run mcp-inspector.
```
npx modelcontextprotocol/inspector#0.17.5
```
From the MCP Inspector menu, connect to your agentgateway address as follows:
- Transport Type: Select Streamable HTTP.
- URL: Enter the agentgateway address, port, and the /mcp path. If your agentgateway proxy is exposed with a LoadBalancer server, use http://<lb-address>/mcp. In local test setups where you port-forwarded the agentgateway proxy on your local machine, use http://localhost:8080/mcp.
- Click Connect.
From the menu bar, click the Tools tab, then click List Tools.
Test the tools: Select a tool, such as echo. In the message field, enter a message, such as Hello, world!, and click Run Tool.

Cleanup

You can remove the resources that you created in this guide.

kubectl delete Deployment mcp-server-everything
kubectl delete Service mcp-server-everything
kubectl delete Backend mcp-backend
kubectl delete HTTPRoute mcp

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