INTEGRATION
Connect AI Agents to the Sage Intacct REST and Web Services API
There is more than one way to reach Sage Intacct programmatically, and the right choice depends on whether you are reading, writing, or connecting an AI client. This is how the REST API, the Legacy XML API, OAuth and the AI Gateway fit together for an AI integration.
- Sage Intacct exposes a modern REST API and an older XML API now labelled Legacy.
- REST is Sage recommended for new work, uses OAuth 2.0 and ships new objects first.
- The AI Gateway and MCP Server, added in 2026 Release 2, give AI clients governed access.
- Use the AI Gateway or MCP Server for reads and a scoped REST key for approved writes.
- ChatFin uses these interfaces and holds the credentials, so integration is governed.
Sage Intacct exposes two programmatic interfaces: a modern REST API that reached general availability in 2025 and is now the direction Sage recommends for new work, and the older XML API that Sage labels Legacy but still supports. New objects and features ship on REST first, while a handful of long standing objects and workflows still live only in the XML layer.
The REST API uses OAuth 2.0, standard HTTP verbs and predictable URLs, with an authorization endpoint under api.intacct.com. A web services ID can hold up to five production keys. On top of these, In 2026 Release 2, shipped on 8 May 2026, Sage added the Sage Intacct AI Gateway: a governed way for external AI tools to reach Intacct data through the REST API and a Sage Intacct MCP Server that speaks the Model Context Protocol. Compatible AI clients can explore metadata, query records and generate insights in natural language under controlled access. So an AI integration has more options than it used to, and the skill is choosing the right one for each job.
The REST API
The REST API uses standard HTTP verbs and predictable URLs, with OAuth 2.0 for authentication and an authorization endpoint under api.intacct.com. It is Sage recommended for new work, and new objects and features ship there first, so it is the default for both reads and approved writes.
A web services ID can hold up to five production keys, so you can keep a narrow read key separate from a narrow write key.
Ask in business terms
The REST API lets an agent work out which Intacct records answer a question phrased the way finance speaks. Nobody has to know the object model first.
To me, that's amazing, where they can just go get the data based on what they know.
Dave Sackett, on the AgentCFO podcast
That is the change worth testing. If a question still needs someone who knows the API, the integration has not done its job.
The Legacy XML API
The XML API is now labelled Legacy, but it is still supported and still necessary for a handful of objects and workflows that have not moved to REST. A robust integration uses REST by default and falls back to XML only where an object requires it.
The AI Gateway and MCP Server
For connecting an AI client, the AI Gateway and the Sage Intacct MCP Server are purpose built. The Model Context Protocol lets a compatible client discover metadata and query records under governed access, which is the cleanest path for read heavy natural language work. See connecting AI securely.
Which interface for which job
Governing the connection
Whatever the interface, the governance is the same: a dedicated integration user, least privilege, separate read and write credentials, secrets stored safely, and a person on every write. The full pattern is on security and governance, and the upgrade safe view is on upgrade safe architecture.
How ChatFin uses them
ChatFin reads through the MCP Server and REST API, writes through a scoped REST key on approval, and falls back to XML only where required. It holds the credentials and keeps a prompt to transaction log, so the integration is governed end to end. ChatFin does not replace Sage Intacct or compete with Sage Copilot. It runs on top of the ERP, and where the AI Gateway, MCP Server and REST API are available it uses them as the governed pipe Sage built. What ChatFin adds is the finance workflow layer: multi step processes from capture to posting, run across every entity, with a human approving each write back and a full prompt to transaction trail.
The result
A clean AI integration reads through the governed pipe, writes through a scoped key with a human step, and uses each interface for what it does best. That is the foundation everything else in this cluster runs on.
Connect AI to Sage Intacct the Right Way
Sage Intacct offers a REST API, a Legacy XML API, and now an AI Gateway and MCP Server. The right integration reads through the governed pipe and writes through a scoped key on approval.
ChatFin uses these interfaces and keeps the connection governed. Book a demo to see it on your instance.