Parameter References

Syntax

A reference starts with $. and can be used in any step parameter:

Reference	Value	Example
`$.inputs.<name>`	A workflow input	`$.inputs.photo`
`$.<step_id>.primary`	The step’s main result	`$.restyle.primary`
`$.<step_id>.output`	The step’s full result	`$.restyle.output`
`$.<step_id>.primary.<field>`	A field inside an object result	`$.product.primary.output.title`
`[n]`	An item in a list	`$.product.primary.output.images[0]`

{{inputs.prompt}} is not a reference. Double braces are sent to the model as literal text.

Whole values and text

A parameter that is exactly one reference keeps the referenced value’s type, such as a URL, a number, a list or an object:

"image_urls": ["$.inputs.photo"],
"price": "$.product.primary.output.price"

A reference inside a longer string is inserted as text:

"prompt": "Restyle this photo as $.inputs.style. Keep the person's face unchanged."

A reference ends at a space or punctuation, so it can end a sentence ($.inputs.style. followed by a space). Write a space after the full stop: $.inputs.style.Keep would be read as one longer path.

What `primary` holds

Step	`primary`	Read text or fields with
Image or video model	The file URL (the first one if the model returns several)	`$.step.primary`, `$.step.output[1]`
`eachlabs-llm-router`	The chat completion object	`$.step.primary.choices[0].message.content`
`eachlabs-http-step`	The response: `status_code` and `output` (the parsed JSON body)	`$.step.primary.output.<field>`
A `choice` step	The result of the branch that ran	`$.choice_id.primary`, `$.choice_id.selected` (branch name)

Prompt fields and whole references

If a prompt-like parameter (prompt, user_prompt, system_prompt, text, content, message, caption, title or description) is exactly $.step.primary or $.step.output, the value arrives JSON-encoded, so a string comes wrapped in quotes. Reference a deeper field, or embed the reference in a sentence:

"prompt": "$.write_prompt.primary.choices[0].message.content"
"prompt": "Use the product from the second image. $.write_scene.primary.choices[0].message.content"

Lists and optional inputs

Empty strings and null values are dropped from lists. An optional input with "default_value": "" can therefore sit in a list and disappears when the caller leaves it out:

"image_urls": ["$.inputs.photo1", "$.inputs.photo2"]

Parallel branches

After a parallel step, reference each branch step by its own id:

{
  "id": "clip",
  "type": "model",
  "model": "bytedance-seedance-2-0-reference-to-video-fast",
  "params": {
    "prompt": "The two people from the reference images walk side by side through a sunny market.",
    "image_urls": ["$.edit_a.primary", "$.edit_b.primary"]
  }
}

Conditions

A choice condition uses the same paths in its expression:

{
  "expression": "$.subject.primary.choices[0].message.content",
  "operator": "string_matches",
  "value": "*PET*"
}

See condition operators.

When a reference fails

A run is rejected if a step references an input that wasn’t sent and has no default_value.
References to steps are checked when the workflow runs, not when you save it. A step can only use inputs and steps that ran before it.
Use brackets for list items: $.step.output[0], not $.step.output.0.

The overview examples use every pattern on this page and were run end to end.

Overview

Concepts

API Reference

OpenAPI Reference

Webhooks

Examples

Parameter References

Syntax

Whole values and text

What `primary` holds

Prompt fields and whole references

Lists and optional inputs

Parallel branches

Conditions

When a reference fails

​Syntax

​Whole values and text

​What primary holds

​Prompt fields and whole references

​Lists and optional inputs

​Parallel branches

​Conditions

​When a reference fails

Syntax

Whole values and text

What `primary` holds

Prompt fields and whole references

Lists and optional inputs

Parallel branches

Conditions

When a reference fails