whentofly — flight search for AI agents (MCP)

whentofly.io is a flexible-date flight search your AI agent can use directly. Ask your agent "cheapest round trip from Singapore to Tokyo in October, 5–9 days" — it searches a whole date window, returns the cheapest real fares with booking links, and tells you whether the price is actually good for that route (a verdict built from historical price bands).

No API key. No signup. One tool, hosted remotely — nothing to run locally.

Install

Claude Code

claude mcp add flights https://whentofly.io/mcp?ch=github

Claude Desktop / claude.ai — Settings → Connectors → Add custom connector → https://whentofly.io/mcp?ch=github

Cursor — add to mcp.json:

{
  "mcpServers": {
    "flights": { "url": "https://whentofly.io/mcp?ch=github" }
  }
}

Any other MCP client with remote (streamable HTTP) support: point it at https://whentofly.io/mcp.

ChatGPT — use the whentofly Custom GPT (MCP connectors are Claude/Cursor-side for now).

What the tool does

search_flights — find the cheapest round-trip in a flexible date window:

• Flexible dates: give a month or date range + min/max trip length (e.g. "5–9 days in October") — it scans every valid depart/return combination and sorts by price.
• Price verdict: each result is scored against the route's historical price bands — good / typical / high — so your agent can answer "should I buy now?", not just "what does it cost?".
• Anywhere mode: omit the destination (or say "anywhere") to get the cheapest destinations from your origin — "where can I fly cheapest from Berlin in September?"
• Booking links for every fare, airline names resolved, prices cross-checked against live Google Flights data on fresh searches.

Example prompts

• "Find the cheapest round trip Singapore → Tokyo in October, 5 to 9 days."
• "Where can I fly the cheapest from Berlin for a week in September?"
• "Is $450 a good price for NYC → Lisbon in November? Check flexible dates."
• "Plan me the cheapest 10–14 day trip to Japan in the next 3 months."

Pricing & funding

Free to use, no key. Booking links are affiliate links — commissions fund the service; prices are identical for you. Fares come from cached airline-ticket data cross-checked against Google Flights; always verify the final price on the booking page.

For developers

The same search is available as a plain JSON API — https://whentofly.io/search (docs). This repo hosts documentation for the hosted MCP server; the service itself is closed-source.

Questions / feedback: hello@whentofly.io or open an issue here.