# Validation module, schema and APIkit validation

*MuleSoft Platform Integration Architect Study Guide · Designing and developing Mule applications · Last updated November 13, 2026 · https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect/designing-and-developing-mule-applications/validation-module-schema-and-apikit-validation*

How to pick a Validation module operation and its error type, collect several failures with the All scope, validate XML against XSD or RELAX NG and JSON against a JSON Schema, and tune APIkit's specification-driven request validation without turning it off.

- Certification: Salesforce MuleSoft Platform Integration Architect
- Exam section: Designing and developing Mule applications
- Study guide: https://www.certifyforce.com/study-guide/mulesoft-platform-integration-architect

**Official exam objective:**

> Correctly apply methods for validating data in Mule applications.

## What the exam expects

- Choose the Validation module operation that expresses a rule (IP lists, collections, Boolean expressions) and predict the error type it raises.
- Collect every failure into one error with the All scope and hand the handler the error type it expects.
- Validate XML with the XML module against XSD or RELAX NG, and JSON with the JSON module against a JSON Schema.
- Tune APIkit for REST request validation, such as its multipart size limit, while keeping validation on.

**Validation module:** the module whose operations fail with a `VALIDATION` error when content misses a criterion. **All scope:** a Validation scope that runs nested validations and raises one combined error. **Schema language:** the XML module setting that picks W3C (XSD) or RELAX NG. **APIkit Router:** the APIkit component that validates requests against the API specification ([Validation module](https://docs.mulesoft.com/validation-connector/latest/), [XML Module Reference](https://docs.mulesoft.com/xml-module/latest/xml-reference), [APIkit reference](https://docs.mulesoft.com/apikit/latest/apikit-4-xml-reference)).

## Key facts

| Fact | Detail | Source |
|---|---|---|
| Validation error parent | Every error is a child of `VALIDATION:VALIDATION` | [Validation reference](https://docs.mulesoft.com/validation-connector/latest/validation-documentation) |
| IP filter list | Defined globally and referenced, or inline per validator | [Validation examples](https://docs.mulesoft.com/validation-connector/latest/validation-examples) |
| Is true failure | `VALIDATION:INVALID_BOOLEAN` | [Validation reference](https://docs.mulesoft.com/validation-connector/latest/validation-documentation) |
| Is not empty collection failure | `VALIDATION:EMPTY_COLLECTION` | [Validation reference](https://docs.mulesoft.com/validation-connector/latest/validation-documentation) |
| All scope | Runs every validation; one `VALIDATION:MULTIPLE`; no `validation:exception` | [Validation examples](https://docs.mulesoft.com/validation-connector/latest/validation-examples) |
| Retyping MULTIPLE | Use the scope's Error Mapping | [Validation examples](https://docs.mulesoft.com/validation-connector/latest/validation-examples) |
| XML Schema language | W3C (default) or RELAXNG | [XML Module Reference](https://docs.mulesoft.com/xml-module/latest/xml-reference) |
| XML failure | `XML-MODULE:SCHEMA_NOT_HONOURED` | [XSD validation](https://docs.mulesoft.com/xml-module/latest/xml-schema-validation) |
| JSON failure | `JSON:SCHEMA_NOT_HONOURED` | [JSON schema validation](https://docs.mulesoft.com/json-module/latest/json-schema-validation) |
| APIkit multipart limit | `apikit.multipart.size.limit`, default 268435456 bytes | [APIkit reference](https://docs.mulesoft.com/apikit/latest/apikit-4-xml-reference) |

## Check yourself

- Which two error types can Is allowed ip throw?
- When the validators inside an All scope run, on which thread and why does their order not matter?
- When an APIkit Router leaves `parser` at its default, which parser reads the API?
- Why can validating a very large JSON document with the JSON module's Validate schema be risky?

## Sources

- [Validation Module 2.0](https://docs.mulesoft.com/validation-connector/latest/)
- [Validation Module Examples 2.0](https://docs.mulesoft.com/validation-connector/latest/validation-examples)
- [Validation Module Documentation Reference](https://docs.mulesoft.com/validation-connector/latest/validation-documentation)
- [Validate Documents Against an XSD Schema with the XML Module](https://docs.mulesoft.com/xml-module/latest/xml-schema-validation)
- [XML Module Reference](https://docs.mulesoft.com/xml-module/latest/xml-reference)
- [Validating Documents Against a JSON Schema with the JSON Module](https://docs.mulesoft.com/json-module/latest/json-schema-validation)
- [APIkit for REST Module Reference](https://docs.mulesoft.com/apikit/latest/apikit-4-xml-reference)
- [Idempotent Message Validator](https://docs.mulesoft.com/mule-runtime/latest/idempotent-message-validator)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 6 linked practice questions, and unlimited timed mock exams are included with the MuleSoft Platform Integration Architect pack (USD $19): https://www.certifyforce.com/practice-exams