| TRVL_MCP_TOKEN | No | Bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_READ_TOKEN | No | Read-scoped bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_WRITE_TOKEN | No | Write-scoped bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_OAUTH_INTROSPECTION_URL | No | OAuth token introspection endpoint for HTTP-mode auth (unused in stdio). Optional. |
| TRVL_MCP_OAUTH_CLIENT_ID | No | OAuth client ID for HTTP-mode token introspection (unused in stdio). Optional. |
| TRVL_MCP_OAUTH_CLIENT_SECRET | No | OAuth client secret for HTTP-mode token introspection (unused in stdio). Optional. Secret. |
| TRVL_MCP_OAUTH_AUDIENCE | No | Expected OAuth audience for HTTP-mode token introspection (unused in stdio). Optional. |
| TRVL_MCP_TOOL_MODE | No | Selects which MCP tool set is registered (e.g. smart/full). Optional, defaults to full set. |
| TRVL_MCP_TOOL_TIMEOUT | No | Per-tool-call timeout override. Optional, defaults to the built-in timeout. |
| AFKLM_KEY | No | Air France-KLM API key; unlocks that airline's live fares/award search. Optional, trvl works without it. Secret. |
| AFKLM_OP_REF | No | 1Password reference for the Air France-KLM API key. Optional, alternative to AFKLM_KEY. |
| AFKLM_KEYCHAIN_SERVICE | No | macOS Keychain service name to read the Air France-KLM API key from. Optional, alternative to AFKLM_KEY. |
| AFKL_KLM_COOKIES | No | Session cookies for Air France-KLM award search. Optional, unlocks award-fare lookups only. Secret. |
| SERPAPI_KEY | No | SerpApi API key; unlocks search-engine-backed lookups used by some providers. Optional, trvl works without it. Secret. |
| TRAVELPAYOUTS_TOKEN | No | Travelpayouts API token; unlocks that flight-price data source. Optional, trvl works without it. Secret. |
| TRANSAVIA_API_KEY | No | Transavia API key; unlocks that airline's live fares. Optional, trvl works without it. Secret. |
| TICKETMASTER_API_KEY | No | Ticketmaster API key; unlocks event listings for destinations. Optional, trvl works without it. Secret. |
| FOURSQUARE_API_KEY | No | Foursquare API key; unlocks that place-search data source. Optional, trvl works without it. Secret. |
| OPENTRIPMAP_API_KEY | No | OpenTripMap API key; unlocks that attractions data source. Optional, trvl works without it. Secret. |
| GEOAPIFY_API_KEY | No | Geoapify API key; unlocks that places/geocoding data source. Optional, trvl works without it. Secret. |
| DISTRIBUSION_API_KEY | No | Distribusion API key; unlocks that ground-transport data source. Optional, trvl works without it. Secret. |
| SKYSCANNER_API_KEY | No | Skyscanner API key; unlocks that car-hire data source. Optional, trvl works without it. Secret. |
| TRVL_MCP_TOKEN | No | Bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_READ_TOKEN | No | Read-scoped bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_WRITE_TOKEN | No | Write-scoped bearer token for HTTP-mode auth (unused in stdio). Optional. Secret. |
| TRVL_MCP_OAUTH_INTROSPECTION_URL | No | OAuth token introspection endpoint for HTTP-mode auth (unused in stdio). Optional. |
| TRVL_MCP_OAUTH_CLIENT_ID | No | OAuth client ID for HTTP-mode token introspection (unused in stdio). Optional. |
| TRVL_MCP_OAUTH_CLIENT_SECRET | No | OAuth client secret for HTTP-mode token introspection (unused in stdio). Optional. Secret. |
| TRVL_MCP_OAUTH_AUDIENCE | No | Expected OAuth audience for HTTP-mode token introspection (unused in stdio). Optional. |
| TRVL_MCP_TOOL_MODE | No | Selects which MCP tool set is registered (e.g. smart/full). Optional, defaults to full set. |
| TRVL_MCP_TOOL_TIMEOUT | No | Per-tool-call timeout override. Optional, defaults to the built-in timeout. |
| AFKLM_KEY | No | Air France-KLM API key; unlocks that airline's live fares/award search. Optional, trvl works without it. Secret. |
| AFKLM_OP_REF | No | 1Password reference for the Air France-KLM API key. Optional, alternative to AFKLM_KEY. |
| AFKLM_KEYCHAIN_SERVICE | No | macOS Keychain service name to read the Air France-KLM API key from. Optional, alternative to AFKLM_KEY. |
| AFKL_KLM_COOKIES | No | Session cookies for Air France-KLM award search. Optional, unlocks award-fare lookups only. Secret. |
| SERPAPI_KEY | No | SerpApi API key; unlocks search-engine-backed lookups used by some providers. Optional, trvl works without it. Secret. |
| TRAVELPAYOUTS_TOKEN | No | Travelpayouts API token; unlocks that flight-price data source. Optional, trvl works without it. Secret. |
| TRANSAVIA_API_KEY | No | Transavia API key; unlocks that airline's live fares. Optional, trvl works without it. Secret. |
| TICKETMASTER_API_KEY | No | Ticketmaster API key; unlocks event listings for destinations. Optional, trvl works without it. Secret. |
| FOURSQUARE_API_KEY | No | Foursquare API key; unlocks that place-search data source. Optional, trvl works without it. Secret. |
| OPENTRIPMAP_API_KEY | No | OpenTripMap API key; unlocks that attractions data source. Optional, trvl works without it. Secret. |
| GEOAPIFY_API_KEY | No | Geoapify API key; unlocks that places/geocoding data source. Optional, trvl works without it. Secret. |
| DISTRIBUSION_API_KEY | No | Distribusion API key; unlocks that ground-transport data source. Optional, trvl works without it. Secret. |
| SKYSCANNER_API_KEY | No | Skyscanner API key; unlocks that car-hire data source. Optional, trvl works without it. Secret. |