Comparator Validation Architecture Reference

Overview

Decision Gate enforces comparator correctness in two layers:

Authoring-time strict validation (default-on) in the MCP layer rejects invalid comparator/type combinations before a scenario or precheck runs. F:crates/decision-gate-mcp/src/validation.rs L36-L673 F:crates/decision-gate-mcp/src/tools.rs L2027-L2050 F:crates/decision-gate-mcp/src/tools.rs L2663-L2707
Runtime comparator evaluation in the core returns tri-state results and yields Unknown when evidence types do not match expectations. F:crates/decision-gate-core/src/runtime/comparator.rs L39-L259

Area	File	Notes
Comparator enum + EvidenceQuery	F:crates/decision-gate-core/src/core/evidence.rs L32-L90	Canonical comparator list and query shape.
Runtime comparator semantics	F:crates/decision-gate-core/src/runtime/comparator.rs L39-L308	Decimal-aware ordering, lex/deep behavior, Unknown on mismatch.
Strict validation engine	F:crates/decision-gate-mcp/src/validation.rs L36-L673	Type-class matrix, schema parsing, domain overrides.
MCP tool integration	F:crates/decision-gate-mcp/src/tools.rs L2027-L2050 F:crates/decision-gate-mcp/src/tools.rs L2663-L2707	`scenario_define` + `precheck` invoke strict validation.
Validation config surface	F:crates/decision-gate-config/src/config.rs L1469-L1521	`ValidationConfig` toggles and profile identifiers.
Contract schemas	F:crates/decision-gate-contract/src/schemas.rs L1105-L1129	Comparator schema and annotations.
Tooltips/docs	F:crates/decision-gate-contract/src/tooltips.rs L260-L296	Public-facing comparator and validation behavior.
Generated docs	F:Docs/generated/decision-gate/tooling.md L1-L42 F:Docs/generated/decision-gate/tooltips.json L1-L80	Regenerated after schema/tooltip updates.
MCP validation tests	F:crates/decision-gate-mcp/tests/validation.rs L1-L220	Unit coverage for strict mode.
System tests	F:system-tests/tests/suites/validation.rs L1-L220	End-to-end validation behavior.

MCP validates provider contracts and check schemas. F:crates/decision-gate-mcp/src/tools.rs L2045-L2048
Strict validation enforces comparator/type compatibility and expected-value shape. F:crates/decision-gate-mcp/src/tools.rs L2045-L2048
Implementation: ToolRouter::define_scenario. F:crates/decision-gate-mcp/src/tools.rs L2027-L2093

MCP validates payload against the registered data shape schema. F:crates/decision-gate-mcp/src/tools.rs L2670-L2680
Strict validation enforces condition compatibility against the data shape schema. F:crates/decision-gate-mcp/src/tools.rs L2690-L2692
Implementation: ToolRouter::precheck. F:crates/decision-gate-mcp/src/tools.rs L2663-L2707

Implemented in crates/decision-gate-mcp/src/validation.rs. F:crates/decision-gate-mcp/src/validation.rs L234-L535
schema_type_classes and helpers derive type classes. F:crates/decision-gate-mcp/src/validation.rs L400-L535
comparator_allowances defines allowed/opt-in/forbidden combinations. F:crates/decision-gate-mcp/src/validation.rs L234-L398
validate_expected_value ensures expected-value shapes match schema. F:crates/decision-gate-mcp/src/validation.rs L587-L673

x-decision-gate.allowed_comparators restricts allowed comparators to a subset of the type-class matrix. F:crates/decision-gate-mcp/src/validation.rs L537-L585
x-decision-gate.dynamic_type = true treats the schema as dynamic (no declared type) and allows comparator validation to proceed without a type restriction, subject to config toggles. F:crates/decision-gate-mcp/src/validation.rs L400-L414

Numeric comparisons are decimal-aware (no float rounding). F:crates/decision-gate-core/src/runtime/comparator.rs L148-L277
RFC 3339 date/date-time ordering is supported for string values. F:crates/decision-gate-core/src/runtime/comparator.rs L168-L295
Unsupported comparisons yield TriState::Unknown. F:crates/decision-gate-core/src/runtime/comparator.rs L65-L198
in_set only applies to scalar evidence values; arrays/objects yield Unknown. F:crates/decision-gate-core/src/runtime/comparator.rs L250-L258
Implementation: crates/decision-gate-core/src/runtime/comparator.rs. F:crates/decision-gate-core/src/runtime/comparator.rs L39-L308

Strict validation is default-on. Disabling strict requires validation.allow_permissive = true. F:crates/decision-gate-config/src/config.rs L1472-L1511
Optional comparator families are gated by config toggles. F:crates/decision-gate-config/src/config.rs L1472-L1487
Implementation: crates/decision-gate-config/src/config.rs (ValidationConfig). F:crates/decision-gate-config/src/config.rs L1469-L1521

Comparator schema and annotations are in crates/decision-gate-contract/src/schemas.rs. F:crates/decision-gate-contract/src/schemas.rs L1105-L1129
Public tooltips and guidance are in crates/decision-gate-contract/src/tooltips.rs. F:crates/decision-gate-contract/src/tooltips.rs L260-L296
Regenerate contract artifacts after any validation or comparator changes: Docs/generated/decision-gate/. F:Docs/generated/decision-gate/tooling.md L1-L42 F:Docs/generated/decision-gate/tooltips.json L1-L80

Update comparator semantics in crates/decision-gate-core/src/runtime/comparator.rs. F:crates/decision-gate-core/src/runtime/comparator.rs L39-L308
Update strict validation logic in crates/decision-gate-mcp/src/validation.rs. F:crates/decision-gate-mcp/src/validation.rs L36-L673
Update config toggles in crates/decision-gate-config/src/config.rs if needed. F:crates/decision-gate-config/src/config.rs L1469-L1521
Align schemas/tooltips in crates/decision-gate-contract/src/schemas.rs and crates/decision-gate-contract/src/tooltips.rs. F:crates/decision-gate-contract/src/schemas.rs L1105-L1129 F:crates/decision-gate-contract/src/tooltips.rs L260-L296
Regenerate Docs/generated/decision-gate/ artifacts. F:Docs/generated/decision-gate/tooling.md L1-L42
Update unit + system tests. F:crates/decision-gate-mcp/tests/validation.rs L1-L220 F:system-tests/tests/suites/validation.rs L1-L220