check-invariants

id	check_invariants
name	Check Invariants
description	Evaluate a value against a list of deterministic rule-based invariants.
tags	["demo","validation"]
examples	["{\"value\":\"hello\",\"invariants\":[{\"name\":\"non_empty\",\"check\":\"non_empty\"}]}"]
inputModes	["application/json"]
outputModes	["application/json"]
securityRequirements	[]
inputSchema	{"$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{"value":{},"invariants":{"type":"array","items":{"type":"object","properties":{"name":{"type":"string"},"check":{"type":"string"},"args":{"type":"object"}},"required":["name","check"]}}},"required":["value","invariants"]}
outputSchema	{"$schema":"https://json-schema.org/draft/2020-12/schema","type":"object","properties":{"verdict":{"type":"string","enum":["pass","fail"]},"failures":{"type":"array","items":{"type":"object","properties":{"name":{"type":"string"},"reason":{"type":"string"}},"required":["name","reason"]}}},"required":["verdict","failures"]}

Evaluate value against each entry in invariants. Each entry has a name (free-form label) and a check selecting one of four deterministic rule kinds:

• non_empty — fails on null, empty string, empty array, empty object.
• min_length — args.min required; passes when string/array length ≥ min.
• max_length — args.max required; passes when string/array length ≤ max.
• contains — args.needle required; substring match for strings, element membership for arrays.

The output verdict is "pass" when every invariant passed, otherwise "fail" with one entry per failure in failures. A malformed invariant (unknown check, missing args field) is surfaced as a failure entry rather than aborting the whole evaluation.