OpenChainGraph Suite · CONTRACT A3 · arch #5

Mortgage P&I Verifier

Note (dated 2026-08-04): a chain composes independent computations performed in an analytical order. No step's output is carried into the next step by the execution model; each step computes from its own declared inputs. This is true of every chain on this site, including chains whose per-step copy below reads as a data handoff.

Verify a mortgage's monthly principal-and-interest payment in two stages: TVM annuity computation of the level payment (ART-327), then a session receipt aggregating the run's execution hashes (CRY-05). Pure time-value-of-money mathematics; no regulation applies.

OpenChainGraph · 2 Steps cryptographic mandate Hash-Anchored §4 chain_depth:2 Client-Side · Zero PII
Chain Topology: TVM Annuity → Session Receipt
§4 Execution Hash · Chain Definition Anchor
execution_hash:computing…
Chain Stages · 2 Steps
1 ROOT node
TVM Annuity Calculator art-327-tvm-annuity
Produces pmt, the level monthly principal-and-interest payment via the closed-form annuity factor; rate_pct is the periodic (monthly) rate and nper the total payment count
MCP Call · compute_annuity
{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "compute_annuity",
    "arguments": {}
  },
  "id": 1
}
https://mcp.ainumbers.co/mcp
↓
2 TERMINAL · D2 node
Agent-Action Audit-Trail Aggregator cry-05-agent-action-audit-trail-aggregator
Produces session_receipt_root, the Merkle root over the run's execution_hashes (final stage)
MCP Call · aggregate_execution_receipts
{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "aggregate_execution_receipts",
    "arguments": {}
  },
  "id": 1
}
https://mcp.ainumbers.co/mcp
Export Artifacts
Download the §4 chain definition artifact (hash-anchored composite JSON) or the §13.11 W3C Verifiable Credentials view. Both derive from the chain definition. No new hash is minted. Available after hash computation.

Ask your agent

Copy this paragraph into Claude, OpenClaw, or any MCP-aware agent to run this whole workflow on the server and check one field that answers a real question.

Question: A $400,000 mortgage at 6.5% annual rate for 30 years. What is the monthly principal-and-interest payment?
Run the AINumbers MCP tool `run_chain` with {"chain":"mortgage-pi-verifier"} and read `art-327-tvm-annuity.pmt`.
Re-run with `inputs` for `art-327-tvm-annuity`, reusing the values that result echoed, with `pv` set to 500000. Compare the same field.
Verify: call `verify_execution_hash` (https://mcp.ainumbers.co/mcp) with `claimed_hash` set to `composite_execution_hash` and the full `composite_artifact`.
Ledger, for a human re-check: https://ledger.ainumbers.co/
PII rule: send synthetic or anonymised inputs only. The MCP server runs these kernels and logs no payloads.
Chain page: https://ainumbers.co/chaingraph/chains/mortgage-pi-verifier.html