MCP server environment variables
The packages of 9,137 servers declare environment variables: settings such as an API key that the server reads when it starts. These are the names declared most often.
| Variable | Servers |
|---|---|
LOG_LEVEL | 208 |
MCP_TRANSPORT | 177 |
MCP_LOG_LEVEL | 171 |
MCP_LICENSE_KEY | 146 |
ANTHROPIC_API_KEY | 144 |
AUTH_MODE | 141 |
APIFY_TOKEN | 140 |
OPENAI_API_KEY | 131 |
How to set them
The install block on each server's page writes the variables its package marks as required into the config for your client, with a placeholder for each value. Replace the placeholders with your own values; a server started without a value it needs stops, or answers that it needs a key.