---
id: api-json-schema-conditional-validation
title: 'API JSON Schema Conditional Validation'
schema_type: TechArticle
category: computer-science
language: en
confidence: medium
last_verified: '2026-06-09'
created_date: '2026-06-09'
generation_method: ai_structured
derived_from_human_seed: true
conflict_of_interest: none_declared
is_live_document: false
data_period: static
atomic_facts:
  - id: fact-cs-api-json-schema-conditional-validation-1
    statement: >-
      JSON Schema documentation describes dependentRequired as conditionally
      requiring one property when another property is present.
    source_title: JSON Schema Conditionals
    source_url: https://json-schema.org/understanding-json-schema/reference/conditionals
    confidence: medium
  - id: fact-cs-api-json-schema-conditional-validation-2
    statement: >-
      JSON Schema documentation describes if, then, and else keywords for
      applying subschemas conditionally.
    source_title: JSON Schema Conditionals
    source_url: https://json-schema.org/understanding-json-schema/reference/conditionals
    confidence: medium
  - id: fact-cs-api-json-schema-conditional-validation-3
    statement: >-
      The JSON Schema 2020-12 validation specification defines dependentRequired
      and dependentSchemas validation keywords.
    source_title: JSON Schema 2020-12 Validation
    source_url: https://json-schema.org/draft/2020-12/json-schema-validation
    confidence: medium
completeness: 0.84
known_gaps:
  - Conditional validation behavior depends on draft version, validator configuration, unevaluated properties, oneOf or anyOf interactions, default handling, and how API frameworks translate validation errors.
  - JSON Schema validation proves structural conformance, not authorization, business approval, or side-effect safety.
disputed_statements: []
primary_sources:
  - title: JSON Schema Conditionals
    type: standard
    year: 2026
    url: https://json-schema.org/understanding-json-schema/reference/conditionals
    institution: JSON Schema
  - title: JSON Schema 2020-12 Validation
    type: standard
    year: 2022
    url: https://json-schema.org/draft/2020-12/json-schema-validation
    institution: JSON Schema
  - title: JSON Schema 2020-12 Core
    type: standard
    year: 2022
    url: https://json-schema.org/draft/2020-12/json-schema-core
    institution: JSON Schema
secondary_sources: []
updated: '2026-06-09'
ai_models:
  - gpt-5-codex
---

## TL;DR

Conditional JSON Schema rules help agents avoid invalid API arguments when fields become required only under certain modes, types, or feature combinations.

## Core Explanation

API schemas often express conditional contracts. A payment method may require a routing number only for bank accounts, a deployment request may require a rollback target only when mode is rollback, and a tool call may require one set of fields when a provider is selected and another set for a different provider.

Useful evidence includes schema draft version, conditional keyword, triggering property, selected branch, validation error path, required dependent fields, defaults, and examples that show each valid mode. Agents should preserve the validation output rather than guessing which missing field the server wanted.

Conditional validation is a structural guardrail. It should be combined with authorization, idempotency, dry-run support, and human approval when a valid payload can still create a risky side effect.

## Source-Mapped Facts

- JSON Schema documentation describes dependentRequired as conditionally requiring one property when another property is present. ([source](https://json-schema.org/understanding-json-schema/reference/conditionals))
- JSON Schema documentation describes if, then, and else keywords for applying subschemas conditionally. ([source](https://json-schema.org/understanding-json-schema/reference/conditionals))
- The JSON Schema 2020-12 validation specification defines dependentRequired and dependentSchemas validation keywords. ([source](https://json-schema.org/draft/2020-12/json-schema-validation))

## Further Reading

- [JSON Schema Conditionals](https://json-schema.org/understanding-json-schema/reference/conditionals)
- [JSON Schema 2020-12 Validation](https://json-schema.org/draft/2020-12/json-schema-validation)
- [JSON Schema 2020-12 Core](https://json-schema.org/draft/2020-12/json-schema-core)