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Fare Facts is a remote MCP server at https://farefacts.app/mcp (Streamable HTTP, stateless, no authentication). All six tools are read-only and free.
Setup
Add Fare Facts to Claude as a custom connector:
- In Claude, open Customize → Connectors. On Team and Enterprise plans, an Owner adds connectors for the organization; if you can't add one, ask an Owner.
- Choose Add custom connector, give it a name (for example, Fare Facts), and paste this URL:
https://farefacts.app/mcp - Leave any sign-in or OAuth fields empty. Fare Facts needs no account or login.
- The connector should show Connected. Its page lists the six tools under Tool permissions.
- In a chat, turn it on from + → Connectors and ask a question, for example: Explain these taxes: US ZP AY XF.
Other MCP clients can connect to the same URL using the Streamable HTTP transport.
Tools
list_rights_topics
List US air passenger rights topics (free)
US airline passenger rights: list the topics Fare Facts covers (bumping/denied boarding, refunds for cancellations and schedule changes, delays, meals and hotels, tarmac delays, the 24-hour rule, bag fees, lost or damaged bags, bag tracing, wheelchairs and mobility devices, what sellers must disclose before you buy, and pending rule changes), each with its topic id and a one-line summary. Free: every Fare Facts tool and answer is free, with no account. Takes no input.
Input: none
get_passenger_right
Get a US air passenger right, with sources (free)
US airline passenger rights: the federal rule for one topic (for example refunds when a flight is cancelled, denied boarding, tarmac delays, the 24-hour rule, lost bags, wheelchairs), questions a passenger can raise with the airline, citations and a current-as-of date. It states rules only; it does not calculate bump payment amounts or explain ticket codes. Free: every Fare Facts tool and answer is free, with no account. Names, confirmation codes (record locators), ticket numbers and frequent flyer numbers are not needed or used; the input is only the codes or numbers in the input schema.
Input: topic: Topic id; the allowed ids are the values listed in this schema.
calculate_bump_compensation
Calculate US denied boarding (bump) compensation (free)
US airline passenger rights: denied boarding compensation calculator for an involuntary bump from an oversold flight under 14 CFR 250.5. Returns the tier (0%, 200% or 400%), the formula result and the cap applied, the right to cash instead of a voucher, the exceptions, and the regulation's definition of fare. It covers involuntary bumps only, not volunteers, who negotiate their own deal with the airline. Free: every Fare Facts tool and answer is free, with no account. Names, confirmation codes (record locators), ticket numbers and frequent flyer numbers are not needed or used; the input is only the codes or numbers in the input schema.
Input: one_way_fare_usd: One-way fare in US dollars to the passenger's destination or first stopover (a planned break of more than 4 hours), including all mandatory taxes and fees but not optional extras such as seat or bag fees. This is how 14 CFR 250.1 defines "fare". An award or other zero-fare ticket is 0.; route: domestic = within the US; international_from_us = an international flight departing a US airport.; alternate_arrival_delay_hours (optional): How many hours after the original flight's planned arrival the alternate flight the airline offered is planned to arrive (at the destination or first stopover). Omitted when no alternate flight was offered.
explain_tax_codes
Explain US airline ticket tax and fee codes (free)
US airline ticket taxes and fees: explain two-character tax codes from a ticket receipt (for example US, ZP, AY, XF, YC, XY, XA), with each amount, its effective date and its source (detail 'full' adds every note). Codes not in the verified list are reported as such, never guessed. Fare basis codes are not covered. Free: every Fare Facts tool and answer is free, with no account. Names, confirmation codes (record locators), ticket numbers and frequent flyer numbers are not needed or used; the input is only the codes or numbers in the input schema. The input is the codes alone, for example ["US","ZP","AY","XF"].
Input: codes: 1 to 20 two-character tax codes from the ticket's tax box.; detail (optional): Optional. "brief" (default) gives the main facts; "full" adds every note we have.
explain_fare_basis
Explain an airline fare basis code (free)
US airline tickets, how to read them: explain a fare basis code (for example KL7NR3). Returns the booking class from the first letter, labeled notes that match the rest of the code (detail 'full' lists every convention), and a tip to paste the fare rules from your own booking for exact change and refund terms. Tax codes are not covered. Free: every Fare Facts tool and answer is free, with no account. Names, confirmation codes (record locators), ticket numbers and frequent flyer numbers are not needed or used; the input is only the codes or numbers in the input schema.
Input: fare_basis: The fare basis code only, 1 to 15 characters.; airline (optional): Optional 2-character airline code, for example AA, DL, UA or B6.; detail (optional): Optional. "brief" (default) gives the main facts; "full" adds every note we have.
get_missing_miles_link
Get an airline's missing miles request link (free)
US airline frequent flyer programs: where and how to request missing miles or points for a past flight (American, Delta, United, JetBlue, Alaska/Hawaiian, Southwest, Frontier, Spirit), with the waiting period, deadline, login needs and a basic economy caveat. Passenger rights rules are not covered. Free: every Fare Facts tool and answer is free, with no account. Names, confirmation codes (record locators), ticket numbers and frequent flyer numbers are not needed or used; the input is only the codes or numbers in the input schema.
Input: airline: The airline whose program you are asking about.
What the tools receive
Only short inputs such as a topic id, a fare amount, tax codes, a fare basis code or an airline name. Names, confirmation codes, ticket numbers and frequent flyer numbers are not needed. If you upload a ticket, Claude reads it and sends only the codes. We log only the tool name, success or failure, and how long it took. See the privacy policy.
Data sources
Every fact lives in a versioned data file with its source link, source title, check time and verification status. The server never fetches airline or government sites when you ask a question; it reads only its own data. Main sources:
- US federal regulations (eCFR): 14 CFR Parts 250 (denied boarding), 254 (domestic baggage), 259 (tarmac delays, 24-hour rule, customer service plans), 260 (refunds), 382 (passengers with disabilities), 399.84 (price advertising), 158 (passenger facility charges); 7 CFR 354.3 (APHIS fees).
- The US Code: 8 U.S.C. 1356, 26 U.S.C. 4261, 49 U.S.C. 40117, 41712 and 44940.
- The Federal Register, for rule changes, delays and enforcement notices.
- IRS Rev. Proc. 2025-32 (2026 ticket tax amounts), TSA, and CBP fee notices.
- The Montreal Convention 1999 and ICAO's 2024 revised liability limits.
- Airlines' own help pages, for missing-miles requests.
"Current as of" policy
Every answer ends with a Current as of stamp: the oldest check time among the facts used in that answer, so the stamp never claims to be fresher than its oldest part. It is shown in US Eastern Time (for example "Nov 10, 2026, 12:27 AM ET"); facts recorded by date only show just the date. Answers also list their source links and end with: General information, not legal advice. Airline policies and government rules change, and which version applies depends on the dates involved (when you bought the ticket, when you flew, or when the problem happened). Check the airline's contract of carriage and the US DOT for your situation.
Dataset version 1.0.0, last full review 2026-11-10. Tax amounts change on two calendars: IRS amounts each January 1, and CBP and APHIS fees each October 1. Each amount shows the date it took effect.
Verification statuses
| Status | Meaning | How answers show it |
|---|---|---|
| verified | Confirmed on a primary source (regulation, statute, official notice or the airline's own page). | Stated as fact, with a citation. |
| secondary | From a reputable secondary source. | Stated with "(secondary source)". |
| unverified | Not yet confirmed. | Never stated. The answer says "not yet verified" and links to the official source. |
| owner_review | Waiting for review by our tariff specialist. | Never stated until approved. |
Tariff notes
Notes on fare basis conventions, receipt formats, tax code meanings and how to tell a tax code from an airline code are written by Fare Facts' owner, a former airline tariff coder. Notes that describe industry conventions may vary by airline, and are labeled that way in answers. Where a note rests on a law or published table, the answer lists that source too. Airline codes can change or fall out of use when airlines merge, are sold or stop flying, so airline-code notes carry the date of their source and are re-checked.
Troubleshooting
- The connector won't connect
- Check that the URL is exactly
https://farefacts.app/mcp(withhttps://and/mcp) and that no sign-in details were entered. Remove the connector and add it again. - Claude doesn't use Fare Facts
- Make sure the connector is turned on for the chat (+ → Connectors), then ask again and mention the topic, for example "US tax codes" or "denied boarding".
- "Invalid input"
- The message says which field is wrong and what's allowed, for example a tax code must be exactly 2 letters or digits. Send only the codes, not the whole ticket.
- "Not yet verified"
- We haven't confirmed that fact against a source yet, so we don't state it. Use the official link shown instead.
- "Not in our verified list"
- We only explain tax codes we have verified, and we don't guess. Ask the airline or ticket seller what the code is.
- The answer is long, or I want every note
explain_tax_codesandexplain_fare_basisgive a brief answer by default. Ask for the full version (detail: "full") to see every note.- Something looks wrong or out of date
- Check the "Current as of" date and the source links on the answer, then email support@farefacts.app with the tool name and the code or topic (never your ticket details).
Support
Email support@farefacts.app for questions or corrections.