Mortgage Calculator

---

version: "2.0.0"

name: Mortgage Calculator

description: "Calculate mortgage payments with equal-principal and equal-interest comparisons. Use when comparing loans, calculating payments, evaluating prepayment."

author: BytesAgain

homepage: https://bytesagain.com

source: https://github.com/bytesagain/ai-skills

---

# Mortgage Calculator

Multi-purpose utility tool for managing structured data entries related to mortgage and financial calculations. Add, list, search, remove, and export data items — all stored locally in a simple log-based format with full history tracking.

Commands

All commands are invoked via `mortgage-calculator <command> [args]`.

| Command | Description |

|---------|-------------|

| `run <args>` | Execute the main function — logs and confirms execution of the specified operation |

| `config` | Show the configuration file path (`$DATA_DIR/config.json`) |

| `status` | Show current status (reports "ready" when the tool is operational) |

| `init` | Initialize the data directory (creates the data folder if it doesn't exist) |

| `list` | List all data entries from the data log file |

| `add <text>` | Add a new dated entry to the data log (auto-prefixed with `YYYY-MM-DD`) |

| `remove <item>` | Remove an entry and log the removal |

| `search <term>` | Search the data log for a keyword (case-insensitive match via `grep -i`) |

| `export` | Export all data from the data log to stdout |

| `info` | Show current version number and data directory path |

| `help` | Show the built-in help message with all available commands |

| `version` | Print version string (`mortgage-calculator v2.0.0`) |

Data Storage

Requirements

When to Use

1. **Financial record keeping** — Use `mortgage-calculator add` to log mortgage-related events (payments made, rate changes, lender communications) and build a local history

2. **Payment tracking** — Record monthly payments, extra payments, or escrow changes with `add`, then review the full log with `list`

3. **Comparison notes** — Store notes from different loan scenarios or lender quotes using `add`, then `search` to find specific terms or rates

4. **Data export for spreadsheets** — Use `mortgage-calculator export` to dump all entries to stdout and redirect to a file for import into Excel or Google Sheets

5. **Automation and scripting** — Integrate `mortgage-calculator add` and `mortgage-calculator export` into shell scripts or cron jobs for automated financial logging workflows

Examples

# Initialize the data directory
mortgage-calculator init

# Add a mortgage payment record
mortgage-calculator add "Monthly payment: ¥4,235.00 — principal ¥2,100 + interest ¥2,135"

# Add a rate change note
mortgage-calculator add "Rate adjusted from 3.85% to 3.50% effective 2025-01-01"

# Add a prepayment record
mortgage-calculator add "Prepayment: ¥50,000 applied to principal, new balance ¥680,000"

# List all entries
mortgage-calculator list

# Search for entries about rate changes
mortgage-calculator search "rate"

# Search for prepayment records
mortgage-calculator search "prepayment"

# Export all data to a file
mortgage-calculator export > mortgage-history.txt

# Check current status
mortgage-calculator status

# Show version and data path
mortgage-calculator info

# Run a custom operation
mortgage-calculator run "quarterly review"

Output

All command output goes to stdout. Redirect to save:

mortgage-calculator list > all-records.txt
mortgage-calculator export > backup.txt

Configuration

Set the `MORTGAGE_CALCULATOR_DIR` environment variable to change the data directory:

export MORTGAGE_CALCULATOR_DIR="$HOME/my-mortgage-data"
mortgage-calculator init

Default location: `~/.local/share/mortgage-calculator/`

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