Build on OneBooks.
A standards-based OAuth 2.0 accounting API with scoped tokens, a developer console with sandbox businesses, an app review program, MCP for AI agents — and a free OneBooks plan for the customers of every partner app.
OAuth 2.0 + PKCE
authorization code, refresh rotation, dynamic registration, device flow
Scoped tokens
read and write scopes per domain — invoices, payments, reports…
Free for your customers
partner-app users get OneBooks at $0
From console to customers.
Register your app
Create it in the developer console and get sandbox businesses to build against.
Build
Standard OAuth 2.0 with PKCE and scopes; documented endpoints for documents, payments and reports; MCP if you're building an agent.
Ship
Submit for review; approved apps connect to any OneBooks business, and your customers get the free plan.
Standards, not surprises.
If you've integrated with any modern OAuth provider, you already know how this works.
- ✓ OAuth 2.0 — authorization code with PKCE, refresh-token rotation, RFC 7591 dynamic registration, RFC 8628 device flow for native apps, RFC 8414 / 9728 discovery.
- ✓ Scopes per domain — invoices, payments, purchases, reports and more, read or write, consented per business.
- ✓ Idempotency everywhere — every financial write accepts an idempotency key, so retries are safe.
- ✓ MCP for agents — the same authorization surface exposes typed tools for AI agents, with human-confirmed writes.
- ✓ Sandbox businesses — build and test without touching real books.
Give your customers accounting, free.
Partner apps don't just integrate — their customers get the full OneBooks product at no cost.
- ✓ Free plan for partner customers — the whole product, forever.
- ✓ App review — unreviewed apps connect to their own sandboxes; approved apps connect to any business.
- ✓ Developer console — credentials, scopes, sandboxes and review status in one place.
- ✓ White-glove onboarding — our team works with yours through integration, mapping and launch.
Developer platform — common questions
What auth does the API use?
OAuth 2.0 — authorization code with PKCE for apps, dynamic client registration for self-service clients, the device flow for native apps without a redirect, and refresh-token rotation throughout.
Is there a sandbox?
Yes — the developer console provisions sandbox businesses so you can build and test against realistic books without touching a customer's data.
How do my customers get the free plan?
Once your app is approved, any business that connects it is placed on the Free plan automatically — the full product, no feature cuts.
Can I build an AI agent on it?
Yes — OneBooks exposes an MCP server on the same OAuth surface, with typed tools, scoped access and human-confirmed writes.
Build the integration your customers are asking for.
Register in the developer console, build against a sandbox, and give your customers accounting for free.