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Environment Variables

MCPX can be configured via environment variables to control logging, authentication, metrics, configuration paths, and runtime behavior. Below is a list of supported variables, their meaning, expected input, and default values.

LOG_LEVEL​

Description: Sets the logging verbosity for MCPX.
Accepted Values: error, warn, info, http, verbose, debug, silly
Default: info

AUTH_KEY​

Description: Optional shared secret used for authenticating incoming connections to MCPX. When set, all requests must include the x-lunar-auth-key header matching this value. This will only be effective if auth.enabled is set to true in app.yaml Accepted Values: Any string
Default: None (authentication is disabled)

PORT​

Description: Specifies the port MCPX will bind to for incoming HTTP traffic to MCPX.
Accepted Values: Any valid port number (integer)
Default: 9000

CONTROL_PLANE_HOST​

Description: Sets the host URL of the Lunar AI Gateway MCPX should connect to.
Accepted Values: Any valid URL
Default: http://localhost:9001

ENABLE_METRICS​

Description: Controls whether metrics should be exposed (e.g. for Prometheus scraping).
Accepted Values: true, false (as strings)
Default: true

SERVE_METRICS_PORT​

Description: Defines the port on which MCPX serves its metrics endpoint.
Accepted Values: Any valid port number (integer)
Default: 3000

APP_CONFIG_PATH​

Description: Path to the YAML file containing application-level configuration (e.g., ACLs, rate limits).
Accepted Values: String path to a .yaml file
Default: config/app.yaml

SERVERS_CONFIG_PATH​

Description: Path to the JSON file that defines which MCP servers/tools should be spawned by MCPX.
Accepted Values: String path to a .json file
Default: config/mcp.json