API integration
What is API integration?
API integration is the connection between two software systems that lets them exchange data and trigger actions automatically, without a person copying information from one to the other. One system calls the other’s API—a defined set of operations the second system exposes—and the two stay in step.
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Mechanics
How API integration works
- 01
A request is constructed
Which operation, which fields, which values.
- 02
The request is authenticated
Proving the caller is allowed to make it.
- 03
The receiving system acts
And returns a response.
- 04
The response is interpreted
Did it work, and what came back? Step four is where most integrations quietly go wrong.
Methods
Common API integration methods
| Method | What it is and where it fits |
|---|---|
| REST | Operations over standard HTTP verbs, usually JSON. The dominant style for modern web APIs. |
| Webhooks | The other system calls you when something happens. Event notifications without polling. |
| Polling | Repeatedly asking whether anything changed. Fallback when no webhook exists. |
| Batch / file transfer | Scheduled bulk exchange. Older enterprise systems, large data volumes. |
| iPaaS platforms | Hosted middleware with prebuilt connectors. Business-team-owned integrations. |
Examples
API integration examples
A CRM and a billing system
A new customer record in the CRM creates a corresponding customer in billing, so invoices go to the right entity.
A support tool and an entitlement system
An incoming ticket triggers a check of the account’s support coverage before it is routed.
A marketing platform and a data warehouse
Campaign engagement flows into the warehouse nightly so reporting reflects one version of the truth.
Reconciliation between two systems of record
Yesterday’s transactions are pulled from both sides and differences are flagged.
Each of these is straightforward described in a sentence and full of edge cases in practice—which fields map to which, what happens when one side rejects the record, and what happens when the same operation runs twice.
The difficulty
Why API integration is harder than it looks
Authentication and its lifecycle
Getting a token is easy. Refreshing and rotating it, and keeping it out of places it should not be, is ongoing work.
Schema drift
APIs change. Fields get renamed, requirements get added, behaviour shifts. An integration built against last year’s contract fails against this year’s, often silently.
Success that is not success
A 200 response with an error in the body is a failure that most integrations record as a win. Reading the status code alone is not enough.
Repeat execution
If the same request runs twice—a retry, a timeout, a re-run—does the receiving system perform the action twice? Without idempotency, it usually does.
Agents
What changes when an AI agent makes the call
Traditional integration is written once by a developer who reads the docs, tests against a sandbox, and ships a fixed set of calls. Every request the system will ever make was reviewed by a person.
An AI agent constructs the call at runtime, from a model’s output. The call was not reviewed—it is assembled from what the model inferred about the API, which may be out of date or simply wrong.
The consequence is immediate. An agent acting on a workflow can create, charge, or delete before anyone reads a log.
Older APIs make it much worse. Legacy vendor APIs carry years of overlapping versions, specs that do not match actual behaviour, and sequences nobody documented. A model has no reliable way to know which path your workflow needs.
That is the gap Swytchcode fills: supplying the agent with the correct path for the workflow, then governing execution with authentication, retries, idempotency, validation, and audit.
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