Affirm API
★ Only Publicly Available OpenAPI DocumentPaymentsPayment Processingbasic23 EndpointsREST
For Agents
Run Affirm buy-now-pay-later checkout, capture and refund transactions, and respond to disputes across 23 REST endpoints.
Use for: Create an Affirm checkout for a $499 cart, Capture a previously authorised Affirm transaction, Issue a refund on an Affirm transaction, List recent settlement events for reconciliation
Not supported: Does not handle card-network processing, accounting reconciliation outside of settlement events, or fraud underwriting — use for Affirm BNPL checkout, transaction lifecycle, and dispute workflows only.
Jentic publishes the only available OpenAPI specification for Affirm API, keeping it validated and agent-ready. Affirm is a buy-now-pay-later (BNPL) platform that lets merchants offer instalment financing at checkout. Its v1 API exposes 23 endpoints covering checkouts (store, direct, update, resend), card-based virtual card flows, transactions (authorize, capture, refund, void), settlement events, dispute lifecycle including evidence upload, and supporting file storage. Authentication uses HTTP basic auth with the public_api_key as the username and the private_api_key as the password.
Install Jentic One Beta
Connect the Affirm API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Affirm API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Affirm API.
Create and update checkouts to offer Affirm BNPL at the point of sale
Authorize, capture, refund, and void transactions on Affirm financing
List and read transactions and transaction events for reconciliation
Read settlement events to reconcile merchant payouts
Manage the dispute lifecycle including closing and submitting evidence
Upload and retrieve files used as dispute evidence
Issue and finalize Affirm virtual cards via the /cards endpoints
Use Cases
Patterns agents use Affirm API for, with concrete tasks.
★ Buy-Now-Pay-Later Checkout Integration
Add Affirm financing as a payment method at checkout. POST /checkout/store creates a hosted checkout the customer completes on Affirm, POST /checkout/direct supports a direct flow, /checkout/{checkout_id}/update modifies the cart before the customer confirms, and /checkout/resend re-sends the checkout link. Once the customer authorises, POST /transactions creates the transaction record on the merchant side.
Call POST /checkout/store with cart total $499, currency USD, and items array, then return the checkout URL for the customer
Transaction Lifecycle and Reconciliation
Manage the post-authorisation transaction lifecycle. POST /transactions/{transaction_id}/capture moves an authorisation to a captured charge, /void cancels an authorisation that won't be captured, and /refund issues a partial or full refund. GET /transactions/events streams every state change and GET /settlements/events lets finance reconcile Affirm payouts to merchant transactions.
Call POST /transactions/{transaction_id}/capture with the captured amount, then GET /settlements/events to find when the funds settle
Dispute Handling and Evidence Submission
Respond to chargebacks and disputes through the API. GET /disputes lists open disputes, /disputes/{dispute_id} returns the detail, /disputes/{dispute_id}/evidence accepts evidence files (uploaded first via POST /files), and /disputes/{dispute_id}/close closes the dispute. Useful for ops teams who manage many disputes per week and want to push the workflow into a queue tool.
Call POST /files with the evidence document, then POST /disputes/{dispute_id}/evidence with the returned file id and a written response
AI Agent Affirm Operations
Let an AI agent answer 'has this Affirm transaction settled?' or 'refund this order' inside an internal Slack or admin tool. Through Jentic, the agent searches by intent, loads the matching Affirm schema, and executes with the basic-auth keys isolated in the vault. Useful for support and finance teams that want self-service access without building a bespoke admin panel.
Search Jentic for 'refund an affirm transaction', load /transactions/{transaction_id}/refund schema, and execute with the transaction id and refund amount
Key Endpoints
23 endpoints — jentic publishes the only available openapi specification for affirm api, keeping it validated and agent-ready.
METHOD
PATH
DESCRIPTION
POST
/checkout/store
Create a hosted Affirm checkout
POST
/checkout/direct
Create a direct Affirm checkout
POST
/transactions
Create a transaction from an authorised checkout
POST
/transactions/{transaction_id}/capture
Capture an authorised transaction
POST
/transactions/{transaction_id}/refund
Refund a captured transaction
POST
/transactions/{transaction_id}/void
Void an unauthorised or pre-capture transaction
GET
/disputes
List open disputes
POST
/disputes/{dispute_id}/evidence
Submit evidence for a dispute
POST
/checkout/store
Create a hosted Affirm checkout
POST
/checkout/direct
Create a direct Affirm checkout
POST
/transactions
Create a transaction from an authorised checkout
POST
/transactions/{transaction_id}/capture
Capture an authorised transaction
POST
/transactions/{transaction_id}/refund
Refund a captured transaction
POST
/transactions/{transaction_id}/void
Void an unauthorised or pre-capture transaction
GET
/disputes
List open disputes
POST
/disputes/{dispute_id}/evidence
Submit evidence for a dispute
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
Your Affirm public_api_key and private_api_key are stored encrypted in the Jentic vault and applied as basic-auth credentials at execution time. Agents never see the raw private key in their context.
Intent-based discovery
Agents search by intent (e.g. 'refund an affirm transaction') and Jentic returns the matching v1 operation with its path and body schema, so the agent picks /transactions/{transaction_id}/refund over /transactions/{transaction_id}/void correctly.
Time to first call
Direct Affirm integration: 2-5 days to wire basic auth, sandbox vs production routing, capture/void/refund flows, and dispute evidence upload. Through Jentic: under 2 hours — search, load schema, execute.
Related APIs
Alternatives and complements available in the Jentic catalogue.
Alternative
Stripe
General payment processor that also surfaces Affirm as a payment method
Pick Stripe to consolidate cards, wallets, and BNPL through one processor; pick the Affirm API directly when you need full access to checkout, settlement, and dispute lifecycle
FAQs
Specific to using Affirm API through Jentic.
Why is there no official OpenAPI spec for the Affirm API?
Affirm publishes developer documentation but does not distribute a downloadable OpenAPI 3 specification. Jentic generates and maintains this spec so that AI agents and developers can call Affirm API via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the Affirm API use?
Affirm uses HTTP basic authentication with the public_api_key as the username and the private_api_key as the password, base64-encoded in the Authorization header. Through Jentic the key pair is stored in the vault and applied at execution time.
Does Affirm have a sandbox environment?
Yes. The spec lists two servers — production at https://api.affirm.com/api/v1 and sandbox at https://sandbox.affirm.com/api/v1. Use the sandbox base URL with sandbox keys for integration testing before going live.
How do I capture and refund an Affirm transaction?
After the customer completes a checkout, POST /transactions creates the transaction; POST /transactions/{transaction_id}/capture captures the authorised amount, /refund issues a refund, and /void cancels an authorisation that has not been captured. Each action returns the updated transaction state.
What are the rate limits for the Affirm API?
Affirm applies merchant-tier rate limits but does not declare specific numbers in the spec. HTTP 429 responses indicate the limit has been reached; Jentic surfaces them verbatim so agents can implement back-off.
How do I create a checkout through Jentic?
Run pip install jentic, search Jentic with 'create an affirm checkout for a cart', load the /checkout/store schema, and execute with the cart total, currency, items, and merchant URLs. Jentic injects the basic-auth keys at execution time.
GET STARTED