Compound

Calculate compound interest and investment growth using financial formulas. Use when you need to plan savings, compare rates, or project wealth.

Security Scan

The skill does what it claims (local compound-interest calculations and local history/config storage); nothing in the package tries to contact remote endpoints or request unrelated credentials, but the runtime script honors undocumented DATA_FILE/CONFIG_FILE environment variables that could be used to redirect where data is written.

Purpose & Capability

The name/description (compound interest calculator) match the provided script and SKILL.md. The script implements calculate, compare, schedule, table, export, history, config, etc., and stores data under ~/.compound as described. No unrelated cloud credentials, binaries, or capabilities are requested.

Instruction Scope

SKILL.md and the script are consistent about accepted calculation env vars and that history is stored at ~/.compound/data.jsonl. However, the embedded Python code also reads DATA_FILE and CONFIG_FILE environment variables (os.environ.get) as overrides for the storage/config paths; these two override vars are not documented in SKILL.md. That means an environment could redirect where results/config are read/written without being obvious from the docs.

Install Mechanism

There is no install spec or remote download; the skill is instruction-only with an included local script. No network downloads or archive extraction are performed. The script will run locally using bash/python, which is expected for this kind of tool.

Credentials

The skill does not request secrets or external service credentials and only uses standard local env vars for inputs (PRINCIPAL, RATE, YEARS, etc.). The only proportionality concern is the undocumented DATA_FILE and CONFIG_FILE env overrides in the script: if someone sets those to paths outside the ~/.compound directory (intentionally or accidentally), the script will read/write there. No other sensitive env vars are referenced.

Persistence & Privilege

The skill persistently writes history and a config file under the user's home (~/.compound). This is expected for a calculator with history and configuration. It does not request always:true, does not modify other skills or system-wide agent settings, nor does it run background services.

Assessment

This skill appears coherent and implements a local compound-interest calculator. Before installing/running: 1) Inspect scripts/script.sh yourself (it is included) — the code is local and readable. 2) Note it will create ~/.compound/config.json and ~/.compound/data.jsonl and append calculation history there. 3) Be aware you (or the environment) can override storage paths with DATA_FILE and CONFIG_FILE environment variables (these overrides are not documented in SKILL.md); avoid setting those to sensitive file paths. 4) Run it as a normal user (not root) and ensure Python 3 is available. If you need stronger guarantees, run the tool in a sandboxed environment or review the full script content before use.

Compound — Compound Interest Calculator

Compound is a command-line compound interest calculator that helps you plan investments, compare interest rates, build amortization schedules, and project financial growth over time.

All calculation history is stored in ~/.compound/data.jsonl as JSONL records for future reference and comparison.

Prerequisites

• Python 3.8+ with standard library
• bash shell

Commands

calculate

Calculate compound interest for a given principal, rate, and time period.

Environment Variables:

• PRINCIPAL (required) — Initial investment amount
• RATE (required) — Annual interest rate as percentage (e.g., 5.5)
• YEARS (required) — Number of years
• FREQUENCY — Compounding frequency: daily, monthly, quarterly, annually (default: monthly)
• CONTRIBUTION — Regular contribution amount (default: 0)
• CONTRIB_FREQ — Contribution frequency: monthly, quarterly, annually (default: monthly)

Example:

PRINCIPAL=10000 RATE=7.5 YEARS=20 FREQUENCY=monthly bash scripts/script.sh calculate

compare

Compare multiple interest rate or compounding frequency scenarios side by side.

Environment Variables:

• PRINCIPAL (required) — Initial investment amount
• RATES (required) — Comma-separated list of rates to compare (e.g., "3,5,7,10")
• YEARS (required) — Number of years
• FREQUENCY — Compounding frequency (default: monthly)

schedule

Generate a detailed payment/growth schedule showing balances at each period.

Environment Variables:

• PRINCIPAL (required) — Initial investment amount
• RATE (required) — Annual interest rate as percentage
• YEARS (required) — Number of years
• FREQUENCY — Compounding frequency (default: monthly)
• CONTRIBUTION — Regular contribution amount (default: 0)

table

Display a year-by-year summary table of investment growth.

Environment Variables:

• PRINCIPAL (required) — Initial investment amount
• RATE (required) — Annual interest rate
• YEARS (required) — Number of years
• CONTRIBUTION — Regular contribution (default: 0)

rate

Calculate the required interest rate to reach a financial goal.

Environment Variables:

• PRINCIPAL (required) — Starting amount
• TARGET (required) — Target amount
• YEARS (required) — Time period in years
• FREQUENCY — Compounding frequency (default: monthly)

goal

Calculate how long it takes to reach a savings goal.

Environment Variables:

• PRINCIPAL (required) — Starting amount
• TARGET (required) — Goal amount
• RATE (required) — Annual interest rate
• CONTRIBUTION — Regular contribution (default: 0)

chart

Generate an ASCII chart of investment growth over time.

Environment Variables:

• PRINCIPAL (required) — Initial amount
• RATE (required) — Annual interest rate
• YEARS (required) — Number of years
• WIDTH — Chart width in characters (default: 60)
• HEIGHT — Chart height in lines (default: 20)

export

Export calculation history to a file.

Environment Variables:

• OUTPUT — Output file path (default: stdout)
• FORMAT — Export format: json, csv, jsonl (default: json)
• CALC_ID — Specific calculation ID to export (default: all)

config

View or update default configuration settings.

Environment Variables:

• KEY — Configuration key to set
• VALUE — Configuration value

history

View past calculations with their results.

Environment Variables:

• LIMIT — Maximum entries to display (default: 20)
• SORT — Sort by: date, principal, rate, total (default: date)

help

Display usage information and available commands.

version

Display the current version of the compound tool.

Data Storage

All calculations are stored in ~/.compound/data.jsonl. Each line is a JSON object with fields:

• id — Unique calculation identifier
• timestamp — ISO 8601 creation time
• type — Calculation type (calculate, compare, goal, etc.)
• params — Input parameters
• result — Calculation results (final amount, interest earned, etc.)

Configuration

Config stored in ~/.compound/config.json:

• default_frequency — Default compounding frequency (default: monthly)
• currency_symbol — Currency symbol for display (default: $)
• decimal_places — Number of decimal places (default: 2)

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