Connecting other systems
Four routes, in rough order of how much work they are.
A ready-made integration. Check first — accounting systems, mailboxes, document storage, telephony and more are already built: Integrations. Nothing you write yourself will be cheaper to maintain than something that already exists.
Zapier, for connecting to another SaaS product without writing code: Connect Zapier.
Webhooks, for the *outbound* direction — you want to be told when something changes in DealJourney: Webhooks. If your question is "how do we react when a deal is won", this is the answer, not polling the API.
The REST API, for the *inbound* direction — your system reads or changes DealJourney data: The REST API. Access is granted with an API key and scoped to exactly what that integration needs: Create and manage API keys.
And one that is not an integration at all: Connect an AI assistant to your CRM lets an AI assistant work with your CRM directly, which for many "can it just read our pipeline and tell me…" requests removes the need to build anything.
Webhooks and the API together are the normal shape of a real integration: the webhook tells you something happened, the API call gets the detail and writes back the result.