API DOCUMENTATION

Build with Phase 3 Benefits.

Versioned REST endpoints, webhook events, SSO and SCIM, and request-based sandbox access. The full OpenAPI spec is available on request.

Request sandbox access Integrations overview

# Create an account
POST /v1/accounts
Authorization: Bearer p3_live_xxxxxxxxxxxx
Content-Type: application/json

{
  "employer_id": "emp_8a3f",
  "employee_id": "e_19284",
  "plan_type": "hsa",
  "effective_date": "2026-07-01"
}

REFERENCE

Three calls to a working HSA.

Create an account, fund it, issue a card. The rest of the API is shaped the same way.

# Create an account
POST /v1/accounts
Authorization: Bearer p3_live_xxxxxxxxxxxx
Content-Type: application/json

{
  "employer_id": "emp_8a3f",
  "employee_id": "e_19284",
  "plan_type": "hsa",
  "effective_date": "2026-07-01"
}

# Post a contribution
POST /v1/accounts/:id/contributions

{
  "amount_cents": 25000,
  "source": "payroll",
  "pay_period": "2026-07-15"
}

# Issue a virtual card
POST /v1/cards

{
  "account_id": "acc_4f29",
  "form_factor": "virtual",
  "shipping": "none"
}

RESOURCES

What's available.

SPEC

OpenAPI 3.1 spec

Full schema for every endpoint. Used to generate our docs.

SANDBOX

Sandbox access

Request a test environment to issue virtual cards and post contributions.

SDK

Node, Python, Go SDKs

First-party SDKs with retries, idempotency, and webhook helpers.

WEBHOOKS

Signed event delivery

Replay, dedupe, and documented event schemas.

SSO + SCIM

Identity

OIDC and SAML SSO, with SCIM for member provisioning.

STATUS

Status & changelog

Status page and changelog for every release.

DEVELOPER ACCESS

Get a key.

Sandbox access is available for partners and integration teams. Email us for keys.

[email protected]

Talk to our engineering team.

Bring your stack. We'll scope an integration in a 30-minute call.

Talk to Partnerships