Streamable HTTP Transport

Streamable HTTP transport connects agentgateway to remote MCP servers over HTTP with streaming support for real-time responses.

Overview

Streamable HTTP transport is ideal when:

MCP servers run as standalone HTTP services
You need real-time streaming of responses
The server is accessible over the network
You want stateful sessions with the MCP server

Quick start

# Start an MCP server with streamable HTTP
PORT=3005 npx -y @modelcontextprotocol/server-everything streamableHttp

# Create config.yaml
cat <<EOF > config.yaml
# yaml-language-server: $schema=https://agentgateway.dev/schema/config
binds:
- port: 3000
  listeners:
  - routes:
    - policies:
        cors:
          allowOrigins:
            - "*"
          allowHeaders:
            - "*"
          exposeHeaders:
            - "Mcp-Session-Id"
      backends:
      - mcp:
          targets:
          - name: mcp
            mcp:
              host: http://localhost:3005/mcp/
EOF

# Run agentgateway
agentgateway -f config.yaml

Configuration

Configure a streamable HTTP MCP backend:

# yaml-language-server: $schema=https://agentgateway.dev/schema/config
binds:
- port: 3000
  listeners:
  - routes:
    - policies:
        cors:
          allowOrigins:
            - "*"
          allowHeaders:
            - "*"
          exposeHeaders:
            - "Mcp-Session-Id"
      backends:
      - mcp:
          targets:
          - name: remote-mcp
            mcp:
              host: http://mcp-server:8080/mcp/

Key configuration

Setting	Description
`mcp.host`	The HTTP URL of the MCP server endpoint
`cors.exposeHeaders`	Must include `Mcp-Session-Id` for session management

Example: Multiple MCP servers

Aggregate multiple remote MCP servers:

backends:
- mcp:
    targets:
    - name: server-a
      mcp:
        host: http://mcp-server-a:8080/mcp/
    - name: server-b
      mcp:
        host: http://mcp-server-b:8080/mcp/

Why use agentgateway?

Direct HTTP Connection	With agentgateway
Client manages connections	Gateway handles reconnection and buffering
No authentication	OAuth2, API keys, or custom auth
No access control	Tool-level authorization
Single server per client	Multiple servers aggregated
No metrics	Full observability with OpenTelemetry
Manual session handling	Automatic session management

Verify access

Open the agentgateway UI to view your configuration
Go to Playground to test tools
Click Connect to retrieve available tools from all configured servers
Select a tool and click Run Tool to test

Learn more

SSE Transport