System integrations: custom API connections
Most businesses work with a handful of tools that do not know each other. A CRM, an accounting package, a web shop, a planning tool, an email program. Each works fine on its own, and between those tools sits someone retyping data. An API integration solves that: the tools exchange data themselves, at the moment it is needed, without anyone having to look after it. I build those integrations, usually in n8n, including for software without a ready-made connection.
What an API integration is, in plain language
An API is the way software talks to other software. Almost every modern tool has one: a set of agreements on how to retrieve, add or change data without the regular user interface. An API integration is a piece of automation that uses those agreements to make two or more tools work together. For example: as soon as a deal in your CRM is set to “won”, a client and an invoice are created automatically in your accounting software and your planning tool gets a new project.
For many tools, standard integrations already exist; in n8n alone for more than four hundred apps. I use those where I can. If a tool has no standard integration but does have an API, I build the connection myself. If a tool has no API at all, there are usually alternatives: exchanging files, processing emails or a web form as an intermediate step.
Integrations I build regularly
CRM and accounting
- Clients and deals from HubSpot, Pipedrive or Teamleader to Exact, Moneybird or e-Boekhouden
- Payment status back to the CRM
- No more duplicate client records
Web shop and administration
- Orders from WooCommerce or Shopify to accounting and stock
- Mollie payments matched to the right order
- Shipping status back to the customer
Forms and communication
- Website forms to CRM, mailing list and Slack or Teams
- Appointments from a booking tool to calendar and invoicing
- Client questions from email or WhatsApp to a ticketing system
Other tools I work with: Google Workspace and Microsoft 365, Notion, Airtable, Simplicate, AFAS, Trengo, Mailchimp, ActiveCampaign, Google Ads, Meta Ads, Google Analytics and Search Console. If your tool is not listed, chances are it can still be connected.
How I approach an integration
- Which data, which direction, which moment. We define exactly what needs to go from A to B, when it should happen and which system leads when data differs. That last point prevents most problems later on.
- Access and limitations. I look at the APIs of both tools: what is possible, what is not, how many requests per minute are allowed, which permissions are needed. I only request the access the integration really needs.
- Build with error handling. The integration is built including what should happen when a tool is briefly unreachable, when a record already exists or when a field is empty. An integration that stops at the first exception is not an integration.
- Test with real data. First in a test environment or with a small part of the data, then fully. You check that the result is correct before the integration goes live.
- Monitor and maintain. After go-live I keep an eye on the integration and adjust it when one of the tools changes its API. That happens more often than you would think.
n8n, Make, Zapier or custom code?
For most integrations between well-known tools, n8n is the best choice: many standard integrations, custom code where needed, no cost per task executed and the option to run on your own server. For a few simple connections with low volume, Zapier or Make can be sufficient, especially if you already use them. A fully custom integration in code I only build when volume or complexity demands it; that is rarely necessary and always more expensive to maintain. I recommend what fits your situation, not what I happen to like building most.
What an API integration costs
An integration between two tools with standard connectors usually comes in between 750 and 1,500 euros one-off. Integrations with several systems, two-way traffic or a tool without a standard connector range from 1,500 to 4,000 euros. After that, a fixed monthly fee for maintenance, because an integration is only as reliable as the APIs it depends on: they get new versions, access keys expire and fields change. Maintenance covers monitoring, resolving these kinds of changes and small adjustments as your process changes. See pricing and maintenance.
Frequently asked questions
My software has no API. Can it still be connected?
Often, yes, via a workaround. Many tools can email exports or place files in a shared location; an automation can process those. The other way round, an automation can supply data via an import function or a web form. It is less elegant than a real API integration, but it saves the same manual hours.
What if one of the tools changes its API?
Then I adjust the integration. This is exactly why maintenance is needed: vendors usually announce changes, and by monitoring the integration I see it when something goes wrong before you notice.
Is an integration secure?
An integration uses secure connections and access keys with limited permissions. I never request more access than the integration needs, store keys encrypted and document which data is exchanged. On your own server or in a European data centre, the data stays within the EU.
Can the integration work both ways?
Yes, but two-way traffic requires clear agreements about which system leads when data differs. Otherwise the tools overwrite each other’s data. I work that out in the first step before anything is built.
Which two tools should be talking to each other?
Name the tools and what needs to happen between them. I will let you know whether it can be done, how, and what it costs. Or see the overview of all automations first.