{
      "tool_id": "art-221-llpa-stack",
      "tool_version": "1.0.0",
      "display_name": "LLPA Stack Calculator",
      "mcp_name": "compute_llpa_stack",
      "mandate_type": "compliance_mandate",
      "wave": 38,
      "gpu": false,
      "url": "https://ainumbers.co/chaingraph/art-221-llpa-stack.html",
      "description": "Fannie Mae public LLPA (Loan-Level Price Adjustment) matrix calculator. FICO-by-LTV base grid plus feature surcharges: cash-out refinance, second home, investment property, warrantable condo, subordinate financing. Applies FTHB AMI waiver (SEL-2023-07, up to 1.75 pp reduction for first-time buyers at or below 100% AMI). Table version: FNM-LLPA-2025-11-01 (Fannie Mae public publication). Not check_agency_eligibility_matrix (DU/LPA approval grid) or check_conforming_loan_limit (FHFA size limits).",
      "input_schema_ref": "chaingraph/art-221-llpa-stack.html#manifest",
      "consumes": [
        "art-222-agency-eligibility-matrix"
      ],
      "feeds": [],
      "status": "live",
      "conformance_fixtures": true,
      "compute_capability": "server",
      "compute_images": [{"system":"sha256-source","image_id":"sha256:7221a3468182a878ebf517663153a90e4973b4125fe3d77c8a44789898b785ad","valid_from":"2026-07-10"},{"system":"risc0","image_id":"sha256:a1a0bc89b5b1febaeda3519f6dbade0fa5ac16beeb143c4e1b01689573567bc6","valid_from":"2026-07-04"}],
      "export_capability": [
        "json"
      ],
      "compute_proof_ready": "ready",
      "compute_proof": {
        "type": "ZkVmReceipt",
        "system": "risc0",
        "receiptFormat": "groth16-bn254",
        "imageId": "sha256:a1a0bc89b5b1febaeda3519f6dbade0fa5ac16beeb143c4e1b01689573567bc6",
        "seal": "EB456eyN9ddC0ybQhiu3iGb7Jcdx68roFPgSJkbEvfUufb9sAffKSfY1yc2mMUJpzlFrf0c9EQe466+q6iJnbRdEO1AipCKEGnDlOfoftCo6y9cx8+ogVgwkTQsv4y+JFpJGoYNgLt8mDMZ8Kee4sexJsBZ6hDKGB1CxUgRCFSMu5kXF3mHw7+m+SeUs6CQpQs8jt707kz8zc2LRYUqRmyLKGw0jQwfrhiw91339/5ltmhV9iKRb2Ss5DQKNSjFgKcXhQdL4n/J8CIyg9dghjwVrUaDpLNwdPukQ3YVENvgPN17ylUwGR4ira2h7mjYa6UXVSQLpAA6udpiKE8Cr8g==",
        "journal": {
          "chaingraph_version": "0.4.0",
          "kernel_digest": "sha256:7221a3468182a878ebf517663153a90e4973b4125fe3d77c8a44789898b785ad",
          "output": {
            "base_llpa": 0,
            "components": [
              {
                "label": "Base LLPA (primary)",
                "value": 0
              }
            ],
            "feature_llpa": 0,
            "fico_band": "740+",
            "fthb_eligible": false,
            "fthb_waiver": 0,
            "ltv_band": "<=60",
            "pii_note": "All inputs processed locally in your browser. No data is transmitted.",
            "regulatory_basis": "12 USC 4501 (FHFA charter); Fannie Mae Selling Guide B3-4.1-02; SEL-2023-07 FTHB waiver",
            "table_source": "Fannie Mae LLPA Matrix effective 2025-11-01 (fanniemae.com; public)",
            "table_version": "FNM-LLPA-2025-11-01",
            "total_llpa_pct": 0
          }
        }
      }
    }