Overview

The BankingBridge Rateflow API gives you real-time mortgage pricing from a curated lender network through a single, authenticated HTTP endpoint. By submitting a loan scenario — loan type, purpose, property details, borrower profile, and location — you receive a ranked set of lender rates, APRs, points, and payment estimates in milliseconds.

This guide covers everything you need to go from zero to a live pricing call: authentication, request structure, field definitions, worked examples, response schema, error handling, and best practices.

Example Credentials

The credentials below are for reference only. You will receive your credentials in a separate email.

Field	Value
API Key	uL6aLuwfcq1dUvEZTq3Gv2O0KgorNbYXXXXXXXX
Rateflow ID	XXXX
Endpoint	https://api.bankingbridge.com/rateflow
Swagger Docs	https://bbrid.ge/swagger

How LoanSifter Pricing Works

The Rateflow API sources pricing through LoanSifter, which uses a best execution model. It is important to understand how this affects the results returned:

• Best execution selection: LoanSifter identifies the investor offering the best price at par (100.00) for the given loan scenario. That single investor is then selected as the pricing source.
• Full rate stack from selected investor: Once the best execution investor is identified, the full rate stack from that investor is returned across all price points (rates, points, and APRs).
• Not independent best execution per price point: LoanSifter does not evaluate and select the best investor independently at each individual price point. All pricing results in a single response come from the one investor selected at par.
• Changing the desired price: You can override the par price used for best execution investor selection by passing the productCharacteristics.desiredPrice field in your request (default: 100). This is the price at which LoanSifter evaluates investors to determine best execution. Adjusting this value shifts which investor is selected, and therefore which rate stack is returned.
• Practical implication: The lender_name field will be consistent across all pricing_results objects in a given response. If your use case requires comparing individual price points across multiple investors, additional API calls with different lock_period or points parameters may be needed.

Articles in This Series

1. Overview (this article)
2. Authentication
3. Endpoint Reference
4. Request Body — Field Reference
5. Loan Type Field Values
6. Worked Example — Conventional Purchase
7. Worked Example — Conventional Purchase (First Time Homebuyer / Affordability)
8. Worked Example — Conventional Refinance (Affordability / AMI-Qualified)
9. Worked Example — Jumbo Conventional Purchase (30-Year Fixed)
10. Worked Example — 7-Year ARM Purchase
11. Worked Example — FHA Purchase
12. Worked Example — Non-QM DSCR Purchase
13. Worked Example — VA IRRRL Refinance
14. Response Schema
15. Error Handling
16. Best Practices
17. Support & Resources