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Loan Amortization Calculator (Coprocesseur Déterministe)
x402
Loan Amortization Calculator (Coprocesseur Déterministe) is a paid API for AI agents from x402.laboiteatubes.media, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-10).
Computes a complete French-style constant-payment loan amortization schedule, including monthly payment, total cost of credit, and a full repayment table, with a SHA-256 proof of the result.
Price / call$0.003
Success—
StatusUnknown
How this service works
Trois calculs déterministes destinés aux agents IA : amortissement de prêt, distance orthodromique, conversion d'unités. Chaque réponse porte son résultat, la formule appliquée, ses limites, et une empreinte SHA-256 recalculable — la chaîne exacte qui a été hachée est renvoyée avec, et `POST /verifier` permet de la contrôler gratuitement. Un même appel rend toujours la même empreinte : l'horodatage est exclu du hachage. Le paiement suit le protocole x402 (version 2), en USDC sur Base.
Output
Returns a JSON object with the computed monthly payment (mensualite), total amount repaid, total credit cost, the full month-by-month amortization table (each row showing interest paid, principal repaid, and remaining balance), plus a SHA-256 cryptographic proof covering all inputs and outputs — along with the exact canonical string that was hashed so the result can be independently verified.
Example use cases
Mortgage feasibility check
“I'm considering a 300,000 EUR home loan at 3.8% annual interest over 300 months — what would my monthly payment be and what's the total I'd end up repaying?”
Car loan comparison
“I'm looking at a 25,000 EUR car loan at 5.2% per year over 60 months. Can you show me the full repayment schedule month by month so I know exactly what I'm paying in interest vs. principal?”
Verifiable loan audit for agent pipeline
“Compute the amortization for a 500,000 EUR loan at 2.9% annual rate over 360 months and give me the SHA-256 proof hash so I can verify the result hasn't been tampered with.”
Technical details
Endpoint
GEThttps://x402.laboiteatubes.media/amortissement?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a deterministic, cryptographically verifiable loan amortization calculation — especially in agentic pipelines where auditability matters. The SHA-256 proof makes results independently verifiable without re-calling the API. Prefer this over general-purpose calculators when you need the exact canonical French-style (mensualités constantes) amortization method, a full month-by-month schedule, and confidence that the same inputs always produce the same hash.
Side effects
- Missing required parameters (montant, taux_annuel, or duree_mois) returns a 400 error
- montant outside range 0.01–1,000,000,000 is rejected
- duree_mois outside range 1–600 is rejected
- taux_annuel outside range 0–100 is rejected
- Payment not provided or invalid x402 payment header results in 402 Payment Required
- Network timeout or upstream unavailability returns a 5xx error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"notes": [
"Calcul mené en centimes entiers, arrondi au centime le plus proche à chaque échéance.",
"La dernière échéance est ajustée pour solder exactement le capital.",
"Taux nominal proportionnel (t/12). Ce n'est ni un TAEG ni un taux actuariel : assurance, frais de dossier et garanties ne sont pas inclus."
],
"preuve": {
"note": "L'horodatage `calcule_le` est volontairement exclu de l'empreinte.",
"empreinte": "14be0ebc8d16f4fc4a5cc3884f0a624365a7d468612e9098b0fbc66ae799c673",
"algorithme": "SHA-256",
"chaine_hachee": "{\"entrees\":{\"devise\":\"EUR\",\"duree_mois\":2,\"montant\":200000,\"taux_annuel\":3.5},\"formule_expression\":\"M = C × i / (1 − (1 + i)^(−n)), avec i = t/1200\",\"operation\":\"amortissement\",\"resultat\":{\"cout_total_credit\":875.42,\"derniere_echeance\":100437.71,\"echeancier\":[{\"capital_rembourse\":99854.38,\"capital_restant_du\":100145.62,\"echeance\":100437.71,\"interets\":583.33,\"mois\":1},{\"capital_rembourse\":100145.62,\"capital_restant_du\":0,\"echeance\":100437.71,\"interets\":292.09,\"mois\":2}],\"mensualite\":100437.71,\"nombre_echeances\":2,\"taux_mensuel\":0.0029166667,\"total_rembourse\":200875.42},\"version_formule\":\"amortissement-mensualites-constantes@1.0.0\"}",
"champs_couverts": [
"operation",
"version_formule",
"entrees",
"resultat",
"formule_expression"
],
"canonicalisation": "JSON à clés triées récursivement, sans espace, encodé en UTF-8"
},
"entrees": {
"devise": "EUR",
"montant": 200000,
"duree_mois": 2,
"taux_annuel": 3.5
},
"formule": {
"reference": "Formule standard de l'annuité constante (valeur actuelle d'une suite d'annuités).",
"variables": {
"C": "capital emprunté",
"M": "mensualité constante",
"i": "taux périodique mensuel",
"n": "nombre de mensualités",
"t": "taux annuel nominal en %"
},
"expression": "M = C × i / (1 − (1 + i)^(−n)), avec i = t/1200",
"description": "Prêt à mensualités constantes (amortissement dit « français »). Les intérêts de chaque échéance sont calculés sur le capital restant dû ; le solde de la mensualité amortit le capital."
},
"service": "coprocesseur-deterministe",
"resultat": {
"echeancier": [
{
"mois": 1,
"echeance": 100437.71,
"interets": 583.33,
"capital_rembourse": 99854.38,
"capital_restant_du": 100145.62
},
{
"mois": 2,
"echeance": 100437.71,
"interets": 292.09,
"capital_rembourse": 100145.62,
"capital_restant_du": 0
}
],
"mensualite": 100437.71,
"taux_mensuel": 0.0029166667,
"total_rembourse": 200875.42,
"nombre_echeances": 2,
"cout_total_credit": 875.42,
"derniere_echeance": 100437.71
},
"operation": "amortissement",
"calcule_le": "2026-08-16T08:29:39.319Z",
"version_formule": "amortissement-mensualites-constantes@1.0.0",
"version_service": "1.0.0"
}
}Tags
x402
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