Environment variables

CLI variables

These variables configure mcp behavior:

Variable	Default	Description
MCP_CONFIG_PATH	~/.config/mcp/servers.json	Path to the config file
MCP_TIMEOUT	60	Timeout in seconds for stdio server responses

MCP_CONFIG_PATH

Override the default config file location. Useful for maintaining multiple configs or testing.

MCP_CONFIG_PATH=./test-servers.json mcp --list

MCP_TIMEOUT

How long to wait for a stdio server to respond, in seconds. Increase this for servers that take a long time to initialize (like some npm packages on first run).

MCP_TIMEOUT=120 mcp slack --list

Does not affect HTTP servers (they use reqwest's default timeouts).

Config variables

Environment variables referenced in servers.json with ${VAR_NAME} syntax. These are user-defined and depend on which servers you've configured.

Common examples:

Variable	Service	Description
GITHUB_TOKEN	GitHub	Personal access token
SLACK_TOKEN	Slack	Bot or user OAuth token (xoxb- or xoxp-)
SENTRY_TOKEN	Sentry	Auth token
GRAFANA_TOKEN	Grafana	Service account token
ROAM_TOKEN	Roam Research	Graph API token

Set them in your shell profile (~/.bashrc, ~/.zshrc, etc.):

export GITHUB_TOKEN="ghp_..."
export SLACK_TOKEN="xoxb-..."

Or pass them inline:

GITHUB_TOKEN="ghp_..." mcp github --list