.. _arch_overview_mcp_multicluster:

MCP multi cluster

The MCP multi cluster combines multiple clusters into one, with the primary purpose of aggregating multiple MCP servers into one. It is intended to be used for routes with the MCP router <_config_http_filters_mcp_router> as the terminal filter.

MCP multi cluster provides metadata at the well defined key envoy.clusters.mcp_multicluster with the envoy::extensions::clusters::mcp_multicluster::v3::ClusterConfig <envoy_v3_api_msg_extensions.clusters.composite.v3.ClusterConfig> protobuf. The MCP router extension uses this metadata to discover tools and resources implemented by aggregated MCP servers.

Configuration

The MCP multi cluster is configured using the :ref:ClusterConfig <envoy_v3_api_msg_extensions.clusters.composite.v3.ClusterConfig>.

Example configuration

The following example shows a MCP multi cluster that aggregates two MCP servers:

.. code-block:: yaml

  name: mcp_multicluster
  connect_timeout: 0.25s
  lb_policy: CLUSTER_PROVIDED
  cluster_type:
    name: envoy.clusters.composite
    typed_config:
      "@type": type.googleapis.com/envoy.extensions.clusters.composite.v3.ClusterConfig
      servers:
      - name: build_tools
        cluster: build_tools
      - name: review_tools
        cluster: build_tools
        host_rewrite_literal: "mcp.review_tools.acme.com"

In this configuration Envoy acts as an MCP server aggregating all tools and resources implemented by the
``build_tools`` and the ``review_tools`` MCP servers.