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Validations

This section documents Apistry's built-in validation functions.

Apistry uses validation to enforce a strict architectural boundary:

  • Persistence establishes durable truth
  • Persistence is the execution boundary
  • Validations are deterministic, declarative, and evaluated pre-persistence
  • Validation failures return HTTP 422 Unprocessable Entity

To reduce conceptual overload, validation documentation is split into:

  • Concepts (why/when): Core Concepts → Validation Model (core-concepts/validation-model.md)
  • Reference (how/syntax): Reference → Validation Reference (reference/validation-reference.md)
  • Function catalog (per-validator semantics): the pages listed below

Validation Categories (catalog index)

The list below categorizes validations by architectural role, not implementation detail, so the validation surface stays stable over time.

1. Scalar Value Constraints

Operate on a single value or a pair of values.

2. Cardinality & Presence Constraints

Operate on sets of fields.

3. Conditional State Constraints

Enforce rules based on presence or equality of other fields.

4. Collection & Structural Constraints

Operate on arrays or object structures.

5. Numeric Aggregation Constraints

Operate over collections with numeric aggregation semantics.

6. Format, Locale & Standards Compliance

Validate values against external standards or well-defined formats.

7. Security & Data Hygiene

Protect against malformed or malicious input.

8. External Admissibility Constraints

Validate request admissibility using authoritative external systems.