An API is the door a vendor leaves open. The integration is what walks through it.
An API integration is a connection between two software systems through their published programming interfaces, so data moves between them automatically — a ServiceM8 job becomes a Xero invoice without anyone re-typing it. The API sets the rules: what you can read, what you can write, how often, and what happens when you ask too much.
The definition, using two systems you probably run
An API — application programming interface — is the set of instructions a piece of software publishes so other software can talk to it. An integration is code that uses those instructions to move data between two systems on a schedule or on a trigger. Nothing more mysterious than that.
Take ServiceM8 and Xero. ServiceM8 lets a private integration authenticate with a key in an X-API-Key header, or a public one via OAuth 2.0 with access tokens that last 3,600 seconds before they must be refreshed (ServiceM8 authentication docs). Xero uses OAuth 2.0 throughout. The integration holds both sets of credentials, reads a completed job from one, and writes an invoice to the other.
The word “published” is load-bearing. If a vendor has no API, or a private one, there is no integration — only screen-scraping, which breaks every time a button moves. The integration checker tells you which of the common Australian systems have a usable API before you commit to either.
The limits the vendor sets, and why they decide the design
Every API rations itself, and those rations dictate how an integration must be built. Xero allows 5 concurrent calls, 60 calls a minute and 5,000 a day per connected organisation, with 10,000 a minute across all organisations for a single app (Xero developer limits FAQ). ServiceM8 allows 180 requests a minute and 20,000 a day, tracked separately per app and per account (ServiceM8 developer documentation).
Those numbers sound generous until you design badly. An integration that re-reads every invoice each time it runs will use Xero’s 5,000 daily calls by mid-morning in a business with a few hundred invoices. A good build asks only for what changed since it last looked. That is the difference between an integration that runs for years and one that dies with an HTTP 429 in week two.
MYOB’s developer team stated a default of 8 calls a second and 1,000,000 a day per API key (MYOB community, 2019 — old enough that we re-check it on every build). Stripe versions its API by date; its current version is 2026-08-26.dahlia, and monthly releases are backward-compatible while named major releases are not (Stripe API versioning). Our Xero and ServiceM8 pages record what we have hit in practice.
Native connector, middleware, or custom code
There are three ways to get data from one system to another. Each is right somewhere, and the vendor selling you one will not tell you where the other two win.
- KNDR·01Native connectorThe vendor built it. ServiceM8 to Xero is the classic example. Free or cheap, maintained by someone else, and it does exactly what the vendor decided and nothing else. Use it when it does what you need. Most people should stop here.
- KNDR·02Middleware (Zapier, n8n and their kind)A platform that already speaks to both ends. Zapier lists around 9,000 apps and polls for new data every 15 minutes on its free plan, every 2 on Professional and every minute on Team (Zapier pricing, September 2026). Fast to start, priced per task, and fragile when the process has many branches.
- KNDR·03Custom codeWritten for your process, against the raw APIs. Dearest to start, cheapest per transaction, and yours. Justified when the connector does not exist, the middleware bill has outgrown a build, or the logic has more exceptions than rules. Zapier vs a custom build works the crossover.
What it costs to sit on the other side
Building on someone’s API is not free either, and the price is changing. From 2 March 2026 Xero retired its revenue-share model for app developers in favour of flat tiers: Starter is free for up to 5 connected organisations, Core is $35 AUD a month for 50, Plus $245 for 1,000 and Advanced $1,445 for 10,000, with app certification required from Plus upward and an annual security assessment from Advanced (Xero developer pricing, September 2026).
For a one-business integration that means nothing: five connections is plenty. For anyone selling an integration to hundreds of businesses it is a real line item that did not exist before, and it will flow through to the price you pay for add-ons over the next year or two.
Payments APIs charge on the transaction instead. Stripe’s Australian pricing is 1.7% + A$0.30 per domestic card payment and 3.5% + A$0.30 for international cards, with a further 2% if currency conversion is needed, all inclusive of GST (Stripe AU pricing, September 2026). The integration is free; the money moving through it is not.
Where integrations break
They break at the documentation first. In the Postman 2025 State of the API Report (8 October 2025, over 5,700 respondents), 55% of API teams reported documentation gaps and 93% reported collaboration problems. When a field is undocumented, the integration guesses, and guesses are what fail at 2am.
They break at security second. The same survey found 50.8% of respondents rated unauthorised or excessive API calls their top concern, and 45.95% worried about credential leaks. An integration holds live keys to your accounting system. Where those keys live, who can read them and how they are rotated is not a detail — ownership and security sets out what we do with yours.
And they break when a vendor changes the door. Stripe’s named releases are explicitly not backward-compatible. Xero retires endpoints. ServiceM8 changes throttling. An integration with nobody watching it is a clock counting down to the next breaking change.
The nine systems we have built against
We have built API integrations against Xero, MYOB, QuickBooks Online, ServiceM8, Simpro, Stripe, GoHighLevel, Zapier and n8n. Everything on this page about limits and behaviour comes from those builds and from the vendors’ published documentation, not from a comparison site.
We have not built against AroFlo, Fergus, Tradify, Reckon or the dozen other systems Australian trade businesses run. If your system is one of those, we will say so on the first call, and the integration capability register shows what we know from their published documentation only.
We have also not published measured results — hours saved, errors removed — from integrations in client businesses. When we have them, they will appear with the sample size. Until then, the honest claim is narrower: the joins work, they log what they do, and you own the code.
How to check before you buy
Before you sign up to any software you expect to connect, find its API documentation and read the limits page. If there is no public documentation, assume there is no integration. 83.2% of organisations in the Postman survey had adopted some form of API-first approach; the ones that have not are the ones you will be stuck in.
Then ask what the API cannot do. Reading is nearly always allowed; writing is often restricted; deleting almost never. If your process needs to change a record after it is created — a variation on a plumbing job, a progress claim on a build — check that the API allows an update, not just a create.
Finally, ask who is watching it. An integration that nobody monitors is not an asset, it is a liability with a delay. Every join we build ships with alerting, because the alternative is finding out from a customer.
The questions people actually ask.
01Xero already connects to ServiceM8. Why would I need anything else?
You might not. The native connector is good and free. People come to us when they need something it does not do — a rule about which jobs invoice when, a second system in the chain, a document generated on completion. If the native connector covers it, we will tell you to use it.
02Is an integration a security risk?
It holds keys to your systems, so yes, it is a thing to secure. The questions to ask any builder: where do the credentials live, who can read them, can they be revoked in one place, and does the integration ask only for the permissions it needs. Xero and ServiceM8 both let you scope access; a good build uses the narrowest scope that works.
03What happens when Xero changes its API?
Something in the integration stops working, and you find out from a log if it was built properly or from a customer if it was not. Vendors announce changes in advance; someone has to be reading. Maintenance is part of the cost of owning an integration, and it should be a line on the quote, not a surprise in year two.
Stop bending.
Start shipping.
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