dsh-finance
> Money math toolbox for DeepSeek Harness (dsh) — loan payments with amortization, compound growth projection, and nominal/effective rate conversion. Zero runtime dependencies, pure arithmetic, fully deterministic.
Agents are bad at money math. "What's the monthly payment on a $300k mortgage at 4% for 30 years?" and "how much will $1,000 grow to in 10 years at 5% compounded monthly?" are exactly the questions LLMs miscalculate — compound interest and PMT formulas are easy to misremember, and a wrong answer here is a wrong financial decision. This plugin turns those questions into deterministic tool calls.
Tools
| Tool | Description |
|---|---|
loan_payment | Fixed-rate loan payment (PMT) → monthly payment, total paid, total interest. Optional amortization schedule (capped at 360 rows) and/or a constant extra principal payment per month (shortened term, interest saved). |
compound_growth | Future value of a lump sum with optional monthly contributions (ordinary annuity). Supports daily / monthly / quarterly / semiannually / annually / continuous compounding. Optional year-by-year breakdown (capped at 60 rows). |
rate_convert | Nominal (APR) ↔ effective (EAR) annual rate conversion, incl. continuous compounding (EAR = e^r − 1). |
Why
- LLMs get these wrong — compound interest, PMT and EAR conversions are classic hallucination territory; this plugin provides exact, tested answers.
- Zero runtime dependencies — pure
Matharithmetic, no network, no filesystem, no dynamic evaluation. Safe to run anywhere. - External-anchor tested — headline numbers are verified against published mortgage tables and textbook EAR values (e.g. $300k @ 4% / 30y → $1,432.25; 12% nominal monthly → 12.682503% EAR), never self-roundtrips.
Install
# into the web profile (dsh plugin has no default profile — always pass --profile)
dsh plugin --profile web add github:TYEclipse/dsh-financeVerify the layer mounted:
dsh --profile web --dump-config | grep '=='Usage examples
What's the monthly payment for a $300,000 mortgage at 4% APR over 30 years?
→ loan_payment { principal: 300000, annual_rate_percent: 4, months: 360 }
→ monthly_payment 1432.25, total_interest 215610, total_paid 515610
I have $1,000 and can add $100/month for 10 years at 5% (monthly compounding). What will I have?
→ compound_growth { principal: 1000, annual_rate_percent: 5, years: 10, compounding: "monthly", contribution_per_month: 100 }
→ future_value 17175.24 (contributions 13000, interest 4175.24)
A loan advertises "12% nominal, compounded monthly". What's the real annual rate?
→ rate_convert { rate_percent: 12, input_kind: "nominal", compounding: "monthly" }
→ output_rate_percent 12.682503 (effective EAR)Semantics
- Money rounding: amounts are rounded to cents at the output boundary only; internal amortization iterations carry full precision, and the final payment is adjusted to clear the balance exactly.
- Extra payments: the contract payment stays fixed; the term shrinks. The tool reports
payoff_months,months_savedandinterest_saved. - Compounding:
loan_paymentuses monthly compounding of the APR by convention (mortgage standard).compound_growthconverts any frequency to an effective monthly rate first, so contributions compose exactly.continuoususes e^rt. - Zero interest is handled exactly (no division by zero): payment = principal ÷ months; growth = principal + contributions.
- Validation: every tool validates its inputs and returns
valid: falsewith a precise reason instead of throwing.
Limits (by design)
- No fees, taxes, insurance or escrow — pure amortization math.
- Schedule capped at 360 rows, yearly breakdown at 60 rows (see
truncated). - No currency conversion — all amounts are in one currency unit.
- Rates below −100% are rejected as nonsensical; anything above is computed exactly.
License
MIT
---
中文简介
dsh-finance 是 DeepSeek Harness 的金融数学工具箱：贷款月供计算（含等额本息摊销表、提前还款影响）、复利增长测算（含定投、支持日/月/季/半年/年/连续复利）、名义利率与有效年利率互转。零运行时依赖、纯算术、完全确定性——专治 LLM 在复利与贷款月供上的心算错误。锚点用例全部对照公开贷款表与教材值验证（30 万美元 4% 利率 30 年期月供 $1,432.25；12% 名义月复利 = 12.682503% 有效年利率）。