jsonlogic-validator

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Implement, validate, and test JSONLogic rules for portable business logic. Use when working with JSONLogic syntax, creating rules for conditional logic, validating rule structures, testing rules against data, or converting business requirements to JSONLogic. Triggers on requests to "write jsonlogic", "validate jsonlogic", "create a rule", "business logic as JSON", "conditional logic", or any mention of JSONLogic rules.

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Sourceyonderlab/kota.agent.skills
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NPX Install

npx skill4agent add yonderlab/kota.agent.skills jsonlogic-validator

Tags

Translated version includes tags in frontmatter
jsonlogic-rulesbusiness-logicrule-validationdata-processingconditional-logic

SKILL.md Content

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JSONLogic Validator

Implement and validate JSONLogic rules—portable, JSON-serializable business logic that works across JavaScript, Python, PHP, Ruby, Go, Java, .Net, and C++.

Core Syntax

Every rule: 
{ "operator": [arguments] }
json
{"==": [1, 1]}                              // comparison
{"var": "user.name"}                        // data access
{"and": [{">=": [{"var": "age"}, 18]}, {"var": "active"}]}  // compound

Quick Reference

CategoryOperators
Data
var
, 
missing
, 
missing_some
Logic
if
, 
==
, 
===
, 
!=
, 
!==
, 
!
, 
!!
, 
and
, 
or
Numeric
>
, 
>=
, 
<
, 
<=
, 
+
, 
-
, 
*
, 
/
, 
%
, 
max
, 
min
Array
map
, 
filter
, 
reduce
, 
all
, 
some
, 
none
, 
merge
, 
in
String
cat
, 
substr
, 
in

Workflow

1. Gather Requirements

Clarify:
  • What data fields are available?
  • What conditions determine the outcome?
  • What should the rule return (boolean, value, category)?

2. Write the Rule

Build incrementally from inner expressions outward:
json
// Requirement: "Premium users over 25 get 20% discount, others get 10%"
{
  "if": [
    {"and": [
      {"==": [{"var": "tier"}, "premium"]},
      {">": [{"var": "age"}, 25]}
    ]},
    0.20,
    0.10
  ]
}

3. Validate

Run the validation script (no dependencies required):
bash
node scripts/validate-jsonlogic.js '<rule>' '<data>'
Example:
bash
node scripts/validate-jsonlogic.js '{">=": [{"var": "age"}, 18]}' '{"age": 25}'

4. Test with Cases

Requires: 
npm install json-logic-js
bash
node scripts/test-jsonlogic.js '<rule>' --test-cases '[
  {"data": {"age": 25}, "expected": true},
  {"data": {"age": 15}, "expected": false}
]'

Common Patterns

Null-safe access with default

json
{"var": ["user.name", "Guest"]}

Range check (between)

json
{"<=": [0, {"var": "value"}, 100]}

Multi-condition (all must pass)

json
{"and": [
  {">=": [{"var": "age"}, 18]},
  {"==": [{"var": "status"}, "active"]},
  {"in": [{"var": "role"}, ["admin", "editor"]]}
]}

Grade/tier classification

json
{"if": [
  {">=": [{"var": "score"}, 90]}, "A",
  {">=": [{"var": "score"}, 80]}, "B",
  {">=": [{"var": "score"}, 70]}, "C",
  "F"
]}

Array operations

json
// Sum: reduce with +
{"reduce": [{"var": "items"}, {"+": [{"var": "accumulator"}, {"var": "current"}]}, 0]}

// Filter: keep matching
{"filter": [{"var": "items"}, {">": [{"var": ""}, 10]}]}

// Any match: some
{"some": [{"var": "items"}, {"==": [{"var": ".status"}, "error"]}]}

Truthy/Falsy (differs from JavaScript)

Falsy: 
0
, 
[]
, 
""
, 
null
Truthy: Everything else (including 
"0"
and 
[0]
)

Validation Checklist

Before deploying a rule:
  • Valid JSON syntax
  • All operators spelled correctly
  • Arguments in arrays where required
  • Data paths match actual data structure
  • Edge cases handled (null, empty, missing keys)
  • Tested with representative data samples

References

For complete operator documentation with all arguments and edge cases:
  • See 
    references/jsonlogic-reference.md