---
id: ERR-6
family: RT-ERR
level: extended
profiles: [runtime]
posture: normative-target
added: "1.0"
changed: "1.0"
source: https://flowdrop.io/spec/rules/rt-err/err-6
specification: FlowDrop Workflow Specification 1.0-draft
licence: CC BY 4.0
---

# ERR-6 — A node's output must be serializable throughout

*RT-ERR (Part II) · level: extended · profiles: runtime · added in 1.0*

Checked over the node's whole output, before any unexposed value is filtered out, so a value the node type does not expose is policed exactly like one it does.

## The rule

> **Normative.** This is the rule.
>
> 1. Every leaf of a node's output must be a JSON value: a string, number, boolean, null, an array, or an object with a defined JSON representation.
>
> 2. The check covers the node's full output, including values its type does not expose.
>
> 3. A violation is a node-level error naming the node, its type, the dotted path to the offending leaf and the offending type; the resulting error output is not retryable and follows the ordinary error-edge-or-fail path.

## Why

Recorded under OPEN-19.

## Related rules

- Names: ERR-1, ERR-2

---

Rule identifiers are permanent and are never renumbered. This specification carries
no implementation status: each implementation publishes its own standing against
these rules. Licensed CC BY 4.0.