Runtime Validation

Runtime validation ensures AXAG contracts are honored during agent execution. While static validation catches structural errors, runtime validation catches behavioral violations — an agent attempting an action without meeting preconditions, exceeding parameter constraints, or violating safety boundaries.

Runtime Validation Points

Pre-Execution Validation

Before executing a tool call, the runtime validates:

• Required parameters: All required parameters are present and non-null
• Type constraints: Parameter values match declared types
• Range constraints: Numeric values are within minimum/maximum bounds
• Enum constraints: String values are from declared enum sets
• Format constraints: Values match declared formats (email, date, URI)
• Preconditions: Declared preconditions are checked (where machine-checkable)

Execution-Time Validation

During execution, the runtime enforces:

• Confirmation gate: If confirmation_required=true, ensure user confirmation was obtained
• Approval gate: If approval_required=true, verify approval token from authorized role
• Scope boundary: Ensure the operation stays within declared scope (tenant, user, etc.)
• Idempotency check: For non-idempotent operations, warn if duplicate detected

Post-Execution Validation

After execution, the runtime verifies:

• Postconditions: Declared postconditions are met (where verifiable)
• Side-effects: Declared side-effects occurred as expected
• Error semantics: Error responses follow the declared error schema

Implementation Pattern

AXAGRuntimeValidator — interface

interface AXAGRuntimeValidator {
  validatePreExecution(
    toolCall: ToolCall,
    manifest: ManifestAction
  ): ValidationResult;

  validateConfirmation(
    toolCall: ToolCall,
    confirmationToken: string | null
  ): ValidationResult;

  validateApproval(
    toolCall: ToolCall,
    approvalToken: string | null,
    approverRole: string
  ): ValidationResult;

  validatePostExecution(
    toolCall: ToolCall,
    result: ExecutionResult,
    manifest: ManifestAction
  ): ValidationResult;
}

interface ValidationResult {
  valid: boolean;
  errors: ValidationError[];
  warnings: ValidationWarning[];
}

Error Response Format

When runtime validation fails, the error response follows a standard format:

Validation error response

{
  "error": {
    "code": "AXAG_VALIDATION_ERROR",
    "type": "precondition_failed",
    "message": "Precondition not met: cart must have at least one item",
    "details": {
      "intent": "cart.begin_checkout",
      "failed_precondition": "cart must have at least one item",
      "suggestion": "Add items to cart before beginning checkout"
    }
  }
}

Common Runtime Validation Errors

Error Code	Type	Description
AXAG_MISSING_PARAM	parameter_error	Required parameter not provided
AXAG_INVALID_TYPE	parameter_error	Parameter value has wrong type
AXAG_OUT_OF_RANGE	constraint_error	Numeric value outside min/max
AXAG_INVALID_ENUM	constraint_error	Value not in allowed enum set
AXAG_PRECONDITION_FAILED	precondition_error	Precondition check failed
AXAG_CONFIRMATION_MISSING	safety_error	Confirmation required but not provided
AXAG_APPROVAL_MISSING	safety_error	Approval required but not provided
AXAG_SCOPE_VIOLATION	security_error	Operation outside declared scope
AXAG_TENANT_BOUNDARY	security_error	Cross-tenant access attempt
AXAG_ROLE_INSUFFICIENT	authorization_error	Caller lacks required role