US Mortgage Compliance Core · Cluster ㉑ · OpenChainGraph v0.4
US Mortgage Compliance Core
Six computational tools covering the full US residential mortgage compliance stack: Reg Z Appendix J actuarial APR (Newton-Raphson solver with fractional-period support), TRID fee tolerance classification and cure computation, TRID APR accuracy verification (§1026.22(a) tolerances), QM points-and-fees test (§1026.43(e)(3) five-tier table, version-pinned 2021-2026), QM APR-APOR spread classification (§1026.43(e)(2)(vi)), and version-pinned Reg Z threshold lookup. All regulatory reference tables are baked into the kernels citing primary sources (FR citations, CFPB rule citations). Zero PII. Agent-native via MCP.
TRID · 12 CFR §1026.19 IN FORCE
Reg Z APR · 12 CFR §1026.22 IN FORCE
QM Rule · 12 CFR §1026.43 IN FORCE
Reg Z Appendix J IN FORCE
QM Tables · Version-pinned 2021-2026
HOEPA Thresholds · Version-pinned 2021-2026
First OCG §21.4 Gated Chain Live
FHFA CLL 2026 · Conforming Loan Limits
Fannie Mae LLPA 2025-11-01 · Version-pinned
FHA MIP · HUD 4000.1 · ML 2023-05
VA Funding Fee · 38 USC §3729 · 2025-01-01
ULDD Phase 5 · Public Stencil Only
ALL IN FORCE: TRID disclosure rules (12 CFR §1026.19), Reg Z APR accuracy (§1026.22(a)), Qualified Mortgage rule (§1026.43), Reg Z Appendix J actuarial method, FHFA 2026 conforming loan limits, Fannie Mae LLPA matrix (effective 2025-11-01), FHA MIP grid (HUD ML 2023-05), and VA funding fee table (38 USC §3729, effective 2025-01-01) are all currently in force. Tables are version-pinned. Rerun check_conforming_loan_limit and verify LLPA table_version when annual announcements occur (FHFA Nov; FHA/VA Jan).
EDUCATIONAL: Outputs are decision-support computations. Not legal or compliance advice, not a regulatory filing. Verify QM threshold values against CFPB annual adjustments (Federal Register). Consult qualified mortgage counsel before relying on any result for loan production or remediation decisions.
Entry point: Reg Z threshold lookup
Start here when building any mortgage compliance workflow. Fetches version-pinned QM and HOEPA tables that downstream nodes consume.
Reg Z APR: computation and accuracy
Actuarial APR solver (Appendix J) and APR accuracy verifier (§1026.22(a)). Run the solver first to obtain the actual APR, then pass it to the verifier.
ART-215 · compliance_mandate
Reg Z Appendix J APR Solver
Newton-Raphson APR solver over the Reg Z Appendix J general actuarial equation. Supports regular periodic loans, irregular payment schedules, and fractional first periods (odd days). Advances and payments arrays. Iterates to 0.00001% precision. Outputs apr_pct (4dp), periodic_rate, iterations, converged flag, and finance_charge.
compute_reg_z_appendix_j_apr
IN FORCE · Reg Z Appendix J
ART-217 · compliance_mandate
TRID APR Accuracy Verifier
Verifies APR accuracy per 12 CFR §1026.22(a). Regular transaction: 1/8 pp (0.125%) tolerance. Irregular transaction: 1/4 pp (0.250%) tolerance. Irregular = multiple advances, irregular payment periods, or demand feature. Verdicts: accurate, accurate_overstated_ok, understated_violation, overstated_violation. Flags TRID_APR_UNDERSTATED_VIOLATION.
verify_trid_apr_accuracy
IN FORCE · §1026.22(a)
TRID fee tolerance and cure
Classifies fees into TRID tolerance buckets and computes the cure amount per 12 CFR §1026.19(e)(3).
Qualified Mortgage: points-and-fees and APR-APOR spread
QM test tools per 12 CFR §1026.43(e)(3) (points-and-fees) and §1026.43(e)(2)(vi) + §1026.43(b)(4) (APR-APOR spread). Run points-and-fees first; only proceed to spread if it passes.
ART-218 · compliance_mandate
QM Points and Fees Test
Five-tier QM points-and-fees table per 12 CFR §1026.43(e)(3). Version-pinned 2021-2026 with Federal Register citations. Tier thresholds: ≥$130,461 (3%), ≥$78,277 (5%), ≥$26,092 (8%), ≥$16,058.50 (fixed $2,003), <$16,058.50 (8%) -- 2026 values. Active tier highlighted. Outputs pass/fail and limit. Feeds §21.4 gate in preflight chain.
check_qm_points_and_fees
IN FORCE · §1026.43(e)(3)
ART-219 · compliance_mandate
QM APR-APOR Spread Classifier
Classifies QM APR-APOR spread per §1026.43(e)(2)(vi). First-lien: safe harbor ≤1.5pp, rebuttable 1.5-2.25pp, fail >2.25pp. HPCT threshold 1.5pp first / 3.5pp sub. General QM outer limit 2.25pp first / 6.5pp sub. Flags QM_APR_SPREAD_FAIL, HPCT_LOAN, QM_REBUTTABLE_PRESUMPTION. Three-zone threshold grid.
classify_qm_apr_apor_spread
IN FORCE · §1026.43(e)(2)(vi)
Agency loan sizing and pricing
FHFA conforming loan limit classification, Fannie Mae DU / Freddie Mac LPA agency eligibility, and Fannie Mae LLPA stack. Run limit check first, then eligibility, then LLPA pricing for eligible loans.
ART-223 · compliance_mandate
Conforming Loan Limit Check
FHFA 2026 conforming loan limit classification by unit count and county tier. Baseline: $806,500 (1-unit). High-cost ceiling: $1,209,750 (150% of baseline). AK/HI/GU/VI always receive ceiling treatment. Optional county_limit_override for exact per-county FHFA data. Classifies as conforming, super_conforming, or jumbo. Surfaces loan_program into output for chain gate routing. Table: FHFA-CLL-2026.
check_conforming_loan_limit
IN FORCE · FHFA-CLL-2026
ART-222 · compliance_mandate
Agency Eligibility Matrix
Fannie Mae DU / Freddie Mac LPA eligibility matrix. DTI caps: 50% DU/LPA, 36%/45% manual. Max LTV/CLTV/HCLTV by occupancy and purpose (purchase/rate-term/cash-out). Multi-unit overlays (2-4 unit). Second home 1-unit-only restriction. Returns ELIGIBLE or INELIGIBLE in eligible_flag. Table: FNM-LPA-ELIGIBILITY-2026-01-01.
check_agency_eligibility_matrix
IN FORCE · DU/LPA Grid 2026
ART-221 · compliance_mandate
LLPA Stack Calculator
Fannie Mae public LLPA matrix (FNM-LLPA-2025-11-01). FICO-by-LTV base grid (9 LTV bands x 8 FICO bands). Purpose adjustments: cash-out refinance, second home, investment property. Property overlays: condo, subordinate financing (indexed by LTV band). FTHB waiver: primary purchase only, AMI at or below 100%, up to 1.75 pp waiver. Returns total_llpa_pct and waiver amount.
compute_llpa_stack
IN FORCE · FNM-LLPA-2025-11-01
Government loan programs: FHA, VA
FHA mortgage insurance premium eligibility and cost (HUD 4000.1), VA funding fee (38 USC §3729) and residual income qualification (VA Pamphlet 26-7 Ch.4), and ULDD/ULAD structural lint (public ULDD Phase 5).
ART-224 · compliance_mandate
FHA MIP Eligibility
FHA mortgage insurance premium eligibility and cost per HUD Handbook 4000.1. UFMIP: 1.75% of base loan amount. Annual MIP grid by loan size vs $726,200 threshold, LTV, and term (ML 2023-05 / ML 2024-01). MIP duration: 11 years if original LTV at or below 90%; life-of-loan if above. Qualifying ratios: 31% front-end / 43% back-end. Max LTV by FICO tier (580 for 96.5%; 500-579 for 90%). Table: HUD-MIP-ML2023-05-ML2024-01.
compute_fha_mip_eligibility
IN FORCE · HUD 4000.1 · ML 2023-05
ART-225 · compliance_mandate
VA Funding Fee and Residual Income
VA funding fee per 38 USC §3729 statutory table (first/subsequent use, three down-payment tiers: below 5%, 5-9.99%, 10%+). Purchase: 2.15%/3.30% first/subsequent below 5%. IRRRL flat: 0.50%. Exemption for service-connected disability. Residual income per VA Pamphlet 26-7 Ch.4 Table 41A (NE/MW/SO/WE regions, family size 1-5, $80/additional member). DTI benchmark: 41%. Tables: VA-FF-2025-01-01; VA-PAMPHLET-26-7-CH4-2024.
compute_va_funding_fee_residual
IN FORCE · 38 USC §3729 · 2025
ART-226 · compliance_mandate
ULDD/ULAD Structural Linter
Structural lint of Fannie Mae ULDD Phase 5 and Freddie Mac ULAD required data points and enumerations. Checks 13 required field presence, 9 enum dictionaries, 7 numeric range constraints, ARM conditionality (arm_index_type required for AdjustableRate), and indicator consistency warnings. ULDD Phase 5 mandate effective 2025-07-28. Uses public ULDD/ULAD data dictionaries only, not the membership-licensed MISMO v3.x Reference Model schema. Table: ULDD-PHASE5-ULAD-1.3-2025-07-28.
lint_mismo_uldd_ulad
IN FORCE · ULDD Phase 5 · 2025-07-28
Chains: 4 chains (3 gated, 1 linear)
Four chains cover mortgage compliance, TRID remediation, agency pricing decisioning, and government loan program routing. Chains with §21.4 gates exit early or fork when a condition is met.
mortgage-compliance-preflight (§21.4 gated, 2 gates):
ART-220 [thresholds] → ART-217 [APR GATE: understated_violation → END] → ART-218 [QM fees GATE: fail → END] → ART-219 [spread]
mortgage-apr-accuracy-and-tolerance-cure (linear):
ART-215 [APR solver] → ART-217 [APR accuracy] → ART-216 [TRID cure]
mortgage-agency-pricing-and-eligibility (§21.4 gated, 1 gate):
ART-223 [CLL check] → ART-222 [eligibility GATE: INELIGIBLE → END] → ART-221 [LLPA stack]
mortgage-government-loan-fit (§21.4 fork gate):
ART-223 [CLL + program FORK: loan_program=VA → ART-225; default → ART-224]
Branch A (VA): ART-225 [VA fee + residual] | Branch B (FHA/default): ART-224 [FHA MIP]
Agent integration
All 6 tools are callable via MCP at https://mcp.ainumbers.co/mcp. Use run_chain to execute a chain end-to-end, or call tools individually by mcp_name.
MCP · chain execution
run_chain
Execute mortgage-compliance-preflight or mortgage-apr-accuracy-and-tolerance-cure end-to-end over MCP. Gates in the preflight chain are evaluated server-side. Returns a composite artifact with decisions[], path_taken[], and skipped_by_gate entries for any early-exit branches.
run_chain
MCP · discovery
find_chain / find_tool
Use find_chain with query "mortgage" to discover both chains. Use find_tool with query "trid" or "qm" to discover individual nodes. Returned tool_id values can be passed directly to tools/call.
find_chain · find_tool
Regulatory references
Primary sources baked into the kernels with explicit version pinning.
Reg Z APR (Appendix J): 12 CFR §1026, Appendix J -- actuarial method equation, advances/payments notation, fractional period (odd-day) treatment
TRID APR accuracy: 12 CFR §1026.22(a) -- 1/8 pp regular / 1/4 pp irregular; definition of irregular transaction
TRID fee tolerance: 12 CFR §1026.19(e)(3) -- zero-tolerance, ten-percent-cumulative, no-tolerance-limit buckets; cure timing and amount rules
QM points-and-fees: 12 CFR §1026.43(e)(3) -- five-tier table; annual CFPB adjustments published in the Federal Register (FR Vol. 87, 88, 89, 90 for 2022-2026 thresholds)
QM APR-APOR spread: 12 CFR §1026.43(e)(2)(vi) safe harbor / rebuttable presumption thresholds; §1026.43(b)(4) HPCT definition; §1026.43(e)(3)(ii) fee failure interaction
HOEPA thresholds: 12 CFR §1026.32 -- annual CFPB adjustments; rate-spread triggers and points-and-fees dollar floors
FHFA Conforming Loan Limits 2026: 12 USC 1454 (Freddie Mac Charter §305); 12 USC 1717 (Fannie Mae Charter §304(b)); HERA 2008 §201; FHFA Annual CLL Adjustment -- baseline $806,500 (1-unit); 150% ceiling $1,209,750; AK/HI/GU/VI at ceiling. Source: FHFA FullCountyLoanLimitList2026.xlsx (public). Table: FHFA-CLL-2026.
Fannie Mae Agency Eligibility (DU/LPA): Fannie Mae Selling Guide B3-2-01 (DU eligibility); Freddie Mac Guide Ch.5100 (LPA eligibility) -- DTI caps, LTV/CLTV/HCLTV grids by occupancy and purpose, multi-unit overlays. Table: FNM-LPA-ELIGIBILITY-2026-01-01.
Fannie Mae LLPA Matrix: Fannie Mae Selling Guide B3-4.1-02; LLPA matrix effective 2025-11-01 (public, FNM website) -- FICO-by-LTV base grid, purpose/property/subordinate-financing adjustments; SEL-2023-07 FTHB AMI waiver. Table: FNM-LLPA-2025-11-01.
FHA MIP (HUD 4000.1): 12 USC 1709 (FHA §203(b)); HUD Handbook 4000.1 §II.A.8 -- UFMIP 1.75%; annual MIP grid (ML 2023-05; ML 2024-01); 31%/43% qualifying ratios; FICO-gated max LTV (580 for 96.5%, 500-579 for 90%). Table: HUD-MIP-ML2023-05-ML2024-01.
VA Funding Fee and Residual Income: 38 USC §3729 (funding fee statutory table); 38 CFR Part 36 (VA home loans); VA Pamphlet 26-7 Ch.4 Table 41A (residual income by region and family size); exemption for service-connected disability. Tables: VA-FF-2025-01-01; VA-PAMPHLET-26-7-CH4-2024.
ULDD / ULAD structural lint: Fannie Mae ULDD Phase 5 Data Stencil (public, fanniemae.com; mandate effective 2025-07-28); Freddie Mac ULAD Data Dictionary v1.3 (public, freddiemac.com); Uniform Mortgage Data Program (UMDP); 12 USC 4501 (FHFA). Tool uses public stencils only, not the membership-licensed MISMO v3.x Reference Model. Table: ULDD-PHASE5-ULAD-1.3-2025-07-28.