n8n OpenAPI Node

Custom n8n node that generates its UI and runtime behavior directly from an OpenAPI schema. Point it at any OpenAPI JSON document and the node will:

• Fetch and cache the specification.
• Surface every operation as a selectable action inside n8n.
• Auto-populate query, path, header, and JSON body parameters.
• Execute requests with optional bearer-token authentication.

Prerequisites

• n8n ^1.116.0 (self-hosted with custom nodes enabled).
• Bun ^1.3.0 for local builds.
• Node.js 18+ (for running Bun and the build scripts).
• Access to an OpenAPI 3.x compliant JSON document.

Installation

1. Clone or download this repository into your n8n custom modules folder (commonly ~/.n8n/custom/).

2. Install dependencies:

   bun install
   

3. Build the distributable bundle:

   bun run build
   

   The compiled node (TypeScript -> JavaScript and assets) is written to the dist/ directory so n8n can consume it.

4. Restart your n8n instance. The node appears as OpenApiNode - Dynamic OpenAPI in the node chooser.

Tip: n8n discovers custom nodes by folder name. Ensure the directory is called n8n-nodes-openapi-node when placed inside ~/.n8n/custom/.

Using the Node

1. Provide an OpenAPI document

• Set OpenAPI JSON URL to a publicly reachable spec (e.g. https://petstore3.swagger.io/api/v3/openapi.json).
• The spec is cached in-memory during a workflow run to avoid repeated downloads.

2. Choose an operation

• After the spec loads, Operation lists every path/method pair, displaying the summary plus HTTP verb and route.
• The node builds the operation list dynamically at runtime, so updates to your spec are reflected on reload.

3. Configure parameters

• Use Parameters (Form) to add query, path, header, or body fields.
• Path parameters are required; the node validates they are present before executing.
• For JSON bodies, the node inspects the schema and offers body properties as selectable options.

4. Optional credentials

Create an OpenApiNode (Bearer Token) credential inside n8n and populate:

• Base URL – default base API URL, used if the spec omits servers.
• Bearer Token – token value (the node adds the Authorization: Bearer ... header automatically).

Alternatively, provide an X-API-Key header in the parameter form.

5. Execute the workflow

• GET/HEAD requests never send a body; other methods send JSON when body parameters exist.
• Responses are returned as-is in the node output (resp.data under json).
• When Continue On Fail is enabled, errors are forwarded as { error, message, response }.

Development

• Source TypeScript lives under src/; build artifacts under dist/.
• The build script (bun run build) compiles each entrypoint with Bun, minifies output, and copies static assets.
• Use bun run publish to bump versions, rebuild, and run the helper publish script (adjust it to your release flow).

Common scripts:

bun run build           # Clean build into dist/
bun run version:update  # Sync src/package.json version metadata

Project Structure

• src/nodes/OpenApiNode.node.ts – main node definition, load-options logic, and request executor.
• src/credentials/OpenApiCredential.credentials.ts – bearer token credential used by the node.
• bin/ – helper scripts for building, versioning, and publishing.
• dist/ – generated output consumed by n8n (created after building).

Troubleshooting

• Spec fails to load: ensure the URL is reachable from the n8n host and returns valid JSON.
• Operations missing: confirm the OpenAPI document sets operationId or the combination of method & path is unique.
• 401/403 responses: verify the credential token is valid or add required headers via the parameter form.
• Local specs: host them behind a reachable URL (file paths are not yet supported).

Feel free to tailor the build or credential logic to match your API authentication needs.