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Level 0: resolver Environment
MCP server hosts
An MCP server makes outbound connections on behalf of every agent that calls it. Its egress is assigned its own policy, separate from the agents that use it.
Configuration and reference code for MCP server hosts
Why separate
If an agent and an MCP server share a policy, an approval for one extends to the other. Run the MCP server in its own namespace, VM or container with its own site and policy. Tool descriptions served by the MCP server may be altered; its resolver configuration is not affected by them.
Pattern
Configure the host with the Kubernetes or Docker page. On the agent policy, approve only the MCP server's hostname. The destinations the server reaches are governed by the server's policy.
compose.yaml
services:
mcp-github:
image: ghcr.io/example/mcp-github:latest
dns: ["<mcp-hosts site resolver IPs>"]
agent:
image: ghcr.io/example/agent:latest
dns: ["<agent site resolver IPs>"]
environment:
MCP_SERVER_URL: "http://mcp-github:8080"
Evaluate Agent DNS with your own agent traffic
Deploy on a single policy in learning mode and review the recorded destinations with your team.