Custom API

Call any web API that publishes an OpenAPI (Swagger) description: paste the spec URL, pick an operation, and fill the fields the node builds for you.

Can use a Custom API connection — 

Optional: pick a saved connection in the Credential field when the service needs one.

Create a connection →

What it does

The node downloads the OpenAPI document at OpenAPI spec URL and lists its operations in Operation, shown as METHOD /path — summary. Once you pick one, Parameters shows a field for each path, query and header parameter, and a single body field for a JSON request body. Required fields are marked.

When it runs, it builds the request, sends it to the API’s address (the first server listed in the spec, or the spec’s own site if none is listed), adds your credential the way the spec asks, and returns the response.

Limits:

• JSON specs only. A YAML spec is refused with a clear message.
• Request bodies are JSON only: form-encoded and file-upload bodies are not generated.
• API key, Basic and Bearer security are supported; OAuth2 sign-in is not.
• References inside the same document are followed; references to other files, and allOf/oneOf combinations, are not.

When to use it

• Use a service that has no dedicated node but publishes an OpenAPI spec.
• Get ready-made fields for each endpoint instead of writing URLs and headers by hand.
• Use Http Request instead when the API has no spec, needs a non-JSON body, or you want full control over the request.

Inputs and settings

Setting	Type	What it does
Credential	Credential	Optional. A credential matching the API’s security scheme: Bearer Token for bearer / API-key schemes, Basic Auth for basic.
OpenAPI spec URL REQ(required)	URL	URL of a public OpenAPI (Swagger) JSON document. Grant access, then pick an operation.
Operation REQ(required)	Choice (loaded from your account)	Choose an operation from the spec.
Parameters	Field list	Fields generated from the selected operation (path, query, header and body).

• OpenAPI spec URL must point at the JSON document itself (often ending in openapi.json or swagger.json), not at the human-readable documentation page. Click Grant access next to the field: it allows both loading the spec and calling the API on that site. You can review it later in Settings → Site access; see Permissions and security.
• Fill Parameters with fixed values or expressions, for example status = {{ $input.status }}.

Outputs

• Output

The output is the API’s response: parsed JSON when the API returns JSON, otherwise the raw text. An empty success response (204) returns success: true. Any error status stops the node with an error.

Dependencies and credentials

• Credential (connection): optional. See Create a connection.

Leave Credential empty for public APIs. Otherwise, pick the credential type that matches the API’s security, as described in the spec:

Security in the spec	Credential type	How it is sent
API key in a header	Bearer Token	The key in the named header, for example X-API-Key.
API key in the query	Bearer Token	The key as the named query parameter, for example ?api_key=….
HTTP bearer	Bearer Token	Authorization: Bearer …
HTTP basic	Basic Auth	Authorization: Basic …

See Create a credential.

Example workflow

1. A Schedule trigger runs every morning.
2. Custom API, OpenAPI spec URL https://petstore3.swagger.io/api/v3/openapi.json (click Grant access), Operation GET /pet/findByStatus, Parameters status = available.
3. Limit keeps the first 5 results.
4. Browser Notification shows how many were found.

Common issues

• “The OpenAPI spec could not be read as JSON. Only JSON specs are supported for now.” The URL serves YAML or a web page. Find the JSON version of the spec.
• “Failed to fetch the OpenAPI spec: 404 Not Found”. The spec URL is wrong, or access to the site was not granted.
• “Operation “…” was not found in the spec”. The spec changed since you picked the operation. Pick it again.
• “Custom API Error: 401 Unauthorized” or “403 Forbidden”. The credential is missing, or its type does not match the spec’s security (Bearer Token for API key and bearer, Basic Auth for basic).
• The run is blocked in the web app. This node runs in the browser extension. Install it, or run the workflow from the extension.

Related nodes

• Http Request: any request, with or without a spec.
• HTTP Request Tool: let an AI agent call an API.
• JSON: reshape the response.