n8n

The n8n provider enables testing n8n AI agents and workflows via webhook endpoints. It handles common n8n response formats and supports tool call extraction and session management.

tip

Looking to run Promptfoo from n8n? See Using Promptfoo in n8n Workflows.

Basic Usage

providers:
  - n8n:https://your-n8n-instance.com/webhook/your-workflow-id

Promptfoo sends a POST request with:

{
  "prompt": "..."
}

The provider automatically extracts output from common n8n response formats including output, response, message.content, text, and array responses. To avoid exposing webhook URLs in stored results or console output, URL-backed n8n provider routes use a stable n8n:webhook:<fingerprint> display ID.

Configuration

providers:
  - id: n8n:https://n8n.example.com/webhook/agent
    config:
      method: POST
      headers:
        Authorization: 'Bearer {{env.N8N_API_KEY}}'
      body:
        message: '{{prompt}}'
        userId: '{{userId}}'
      transformResponse: 'json.agent_response'

Config Options

Option	Type	Default	Description
url	string	-	Webhook URL (alternative to provider path)
method	string	POST	GET, POST, PUT, or PATCH; GET encodes body fields as query parameters
headers	object	-	Additional request headers with Nunjucks templating
body	object/string	{prompt}	Request/body-query template; object form is recommended for JSON requests
transformResponse	string	-	JavaScript expression to extract output
sessionHeader	string	-	Request header name for the session ID
sessionParser	string	-	JavaScript expression to extract a session ID
sessionField	string	sessionId	Body field name for a supplied session ID

Response Formats

The provider handles these n8n response patterns:

{ "output": "Response text" }
{ "response": "Agent response" }
{ "message": { "content": "Hello" } }
[{ "json": { "output": "Result" } }]

Successful HTTP responses containing a non-empty error value, including n8n item responses such as [{ "json": { "error": "Workflow failed" } }], are reported as provider errors instead of evaluation output. Empty status values such as false or null do not turn a successful response into an error.

Tool Calls

The provider extracts tool calls from agent responses:

tests:
  - vars:
      prompt: "What's my order status?"
    assert:
      - type: javascript
        value: |
          const toolCalls = context.providerResponse?.metadata?.toolCalls || [];
          return toolCalls.some(tc => tc.name === 'order_lookup');

Supported formats:

{ "tool_calls": [{ "name": "search", "arguments": {...} }] }
{ "actions": [{ "tool": "search", "input": {...} }] }

Session Management

For multi-turn conversations:

providers:
  - id: n8n:https://n8n.example.com/webhook/agent
    config:
      sessionField: conversationId
      sessionParser: 'data.sessionId'

The provider returns extracted session IDs as response.sessionId. Promptfoo's multi-turn strategies scope that value to the current conversation and supply it to subsequent turns as {{sessionId}}; the provider does not share one implicit session between independent test cases. For client-generated sessions, supply sessionId in test variables or through transformVars.

warning

Webhook URLs and responses can contain sensitive workflow data. Put authentication values in templated headers rather than URL query strings or paths, and treat local eval result exports and debug logs as sensitive. The provider hides webhook URLs in its display identifier and does not cache webhook requests or responses, so tokenized URLs and session-bearing payloads do not enter Promptfoo response-cache diagnostics or storage. The shared fetch layer now strips basic-auth credentials and known sensitive query parameters (api_key, token, signature, …) before writing URLs to debug logs, but path-as-secret URLs (/webhook/<unguessable-id>) still appear in those logs by design — keep LOG_LEVEL=debug output out of shared transcripts when running against tokenized webhooks. URLs remain part of your configuration and the outbound request.

For non-idempotent methods (POST / PATCH, the default), the provider passes maxRetries: 0 to the shared fetch helper. Transient network failures fail through to the caller rather than re-delivering a workflow that may have already accepted the request and dispatched side-effects (sending messages, writing to a database). Idempotent methods (GET / PUT) keep the default retry budget.

n8n Variable Conversion

n8n Format	Promptfoo Format
{{ $json.query }}	{{query}}
{{ $json.user.name }}	{{user.name}}

See Also

• Using Promptfoo in n8n Workflows
• HTTP Provider
• Webhook Provider