Custom Apps: turn any REST API into a WordPress integration
Build a private integration for any REST API without writing plugin code, or import a cURL command, an OpenAPI or Swagger spec or a Postman collection and have the actions generated for you. The app then sits in the builder beside the 918+ integrations that ship with FlowMattic.
4 spec formats to import6 authentication types5 HTTP methodsExport and import as JSON
From an API reference to a step in the builder
Three steps, no code, and the app behaves like any other integration from then on.
-
Define
Name it, choose the authentication
Give the app a name and an icon, then pick its default authentication from your Connects: none, Basic Auth, API Key, Bearer Token, OAuth 2.0, AWS Signature V4 or FTP. A step can still pick a different Connect later.
-
Build
Add actions and triggers
Import the actions from cURL, OpenAPI 3.x, Swagger 2.0 or Postman 2.1, or add one by hand with a method, an endpoint, headers, query, path and body parameters. Triggers are webhooks, each with setup instructions for the sending app.
-
Use
Pick it like any integration
The app appears in the step picker with its actions and triggers. Map fields from earlier steps, test the step against real data, and reuse the app in as many workflows as you like.
Import the API instead of typing it
Paste a spec, upload the JSON or YAML, or fetch it from a URL. FlowMattic lists the actions it found, lets you create a new app or append them to an existing one with duplicates skipped, and fills in the body, query, path and header fields from the spec.
- cURL: paste one command from any API documentation, long flags included
- OpenAPI 3.x and Swagger 2.0, as JSON or YAML
- Postman 2.1 collection exports
- FlowMattic App JSON, to restore an export or share an app with another site
Authenticate with a Connect, once
A custom app does not hold credentials itself. It points at a Connect, the same store that integrations use, so a key is pasted or an OAuth consent given once and every action in the app sends it. Credentials stay in your own site database, never on a FlowMattic server.
- Basic Auth, API Key, Bearer Token, OAuth 2.0, AWS Signature V4 and FTP or SFTP Connects
- Choose a default Connect per app and override it on any step
- Dynamic values anywhere: wrap a parameter in double curly braces in the URL, headers or body
- Raw JSON or XML bodies when the API wants one written by hand
In the builder, as an AI tool, and on your other sites
Once saved, the app is listed with every installed integration and its actions can be called by AI agents and MCP clients like any other tool. Export it as JSON to move it to a client site or hand it to a colleague, who imports it in one click.
- Appears in the step picker beside every other app
- Works as a tool for AI agents and for clients of the MCP Server, with its parameters in Configure
- Export App and Import App from the list, as FlowMattic App JSON
- Webhook triggers carry the sender's payload into the workflow the moment it arrives
What a custom app can do
Everything a shipped integration can, defined by you.
Any REST endpoint
GET, POST, PUT, PATCH and DELETE, with custom headers, query strings, path parameters and a body as fields or raw JSON or XML.
Import from a spec
cURL, OpenAPI 3.x, Swagger 2.0 or Postman 2.1, pasted, uploaded or fetched from a URL, with a preview before anything is created.
Six authentication types
Basic, API Key, Bearer, OAuth 2.0, AWS Signature V4 and FTP, stored once as a Connect and reused by every action.
Webhook triggers
Each trigger gets its own webhook URL and the setup instructions you write for the sending app. The payload arrives as mappable fields.
Export and import
Export App writes the whole definition as JSON. Import App restores it on another site, with the data re-validated before it is stored.
Tested and logged like any step
Test a custom action in the step panel, see the response, and find every call later in Task History, with secrets masked and a re-execute button.
Questions about Custom Apps
Do I need to write code to build a custom app?
No. Choose the authentication, fill in the endpoint, method, headers and parameters in a form, and the action is ready. Dynamic values are wrapped in double curly braces. No PHP or JavaScript is involved.
Which authentication methods are supported?
A custom app authenticates through a Connect, so it can use Basic Auth, an API Key, a Bearer Token, OAuth 2.0, AWS Signature V4 or FTP and SFTP credentials, or no authentication at all. Set a default Connect on the app and override it on any step.
Can I import an existing API instead of building it field by field?
Yes. Import actions from a cURL command, an OpenAPI 3.x or Swagger 2.0 spec or a Postman 2.1 collection, pasted, uploaded as JSON or YAML, or fetched from a URL. You see the actions it found before anything is created, and can append them to an app you already have.
Can a custom app start a workflow?
Yes, through webhook triggers. Each trigger gets a webhook URL and the setup instructions you write, and when the app calls that URL the workflow runs with the payload as mappable fields. Polling triggers are not part of custom apps; use the Schedule trigger with an action for that.
Where can I use the app once it is built?
Anywhere an integration works: in any workflow on the site, as a tool an AI agent can call, and as a tool exposed to MCP clients. Export it as FlowMattic App JSON to import on another site.
How is this different from FlowMattic Connects?
A Connect stores one set of credentials; a custom app defines the actions and triggers that use them. FlowMattic Connects is where OAuth consents and API keys live, and a custom app points at one of them.
Did not find your answer? You can browse the help center or ask us directly.
If it has a REST API, it can be a FlowMattic app
Internal tools, niche SaaS, regional platforms and legacy systems join the 918+ integrations on 12,925+ sites.
30-day money-back guarantee Unlimited custom apps Self-hosted