assert

Fail the flow when JMESPath checks on the previous output do not pass

Runs one or more checks against the previous node’s output. On failure, execution throws and the flow stops.

Check path values are JMESPath from the previous root (status, body.id) — not previous.status and not run-input paths (use templates / an input node first). See How flows work.

JMESPath checks or throw. Multiple outgoing edges (fan-out) share the same output.

Data

Field	Type	Description
`label`	string	Optional UI label
`checks`	array	required (min 1)

Check object

Field	Type	Description
`path`	string	JMESPath against previous output
`op`	string	Optional operator (default `truthy`, or `eq` when `equals` is set)
`value`	any	Comparison value for ops that need one
`equals`	any	Legacy alias for `op: "eq"` + `value`

Operators

`op`	Needs `value`	Passes when
`eq`	yes	Deep equal (`JSON.stringify`)
`neq`	yes	Not deep equal
`gt` / `gte` / `lt` / `lte`	yes	Numeric compare when both sides are numbers (or numeric strings); otherwise string compare
`contains`	yes	String includes, or array has a deep-equal element
`notContains`	yes	Inverse of `contains`
`startsWith` / `endsWith`	yes	String prefix / suffix
`matches`	yes	`RegExp(value).test(actual)` on a string (or stringified number/boolean)
`exists`	no	Value is not `null` / `undefined`
`truthy`	no	JavaScript truthiness
`falsy`	no	JavaScript falsiness

Legacy forms still work:

{ "path": "body.id" } → truthy
{ "path": "status", "equals": 200 } → eq

Input / output

	Value
Execute input	Previous node output
Output	`{ "ok": true, "failures": [] }` on success
On failure	Throws `Assertion failed: …`

Examples

Status in 2xx

{
  "id": "assertOk",
  "type": "assert",
  "data": {
    "checks": [
      { "path": "status", "op": "gte", "value": 200 },
      { "path": "status", "op": "lt", "value": 300 }
    ]
  }
}

Body message contains text

{
  "checks": [
    { "path": "body.message", "op": "contains", "value": "created" }
  ]
}

Legacy equals (still valid)

{
  "checks": [{ "path": "status", "equals": 200 }]
}

Multiple checks

{
  "id": "assertLogin",
  "type": "assert",
  "data": {
    "label": "Login ok",
    "checks": [
      { "path": "status", "op": "eq", "value": 201 },
      { "path": "body.id", "op": "exists" },
      { "path": "body.email", "op": "eq", "value": "demo@example.com" }
    ]
  }
}

Nested / object equality

eq (and legacy equals) compares with exact deep equality (JSON.stringify on both sides). The value at path must match fully — same keys, same nested values. Extra fields on the actual value cause a failure.

Prefer asserting fields separately when you only care about some keys:

{
  "checks": [
    { "path": "body.ok", "op": "eq", "value": true },
    { "path": "body.role", "op": "eq", "value": "admin" }
  ]
}