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name: budget-builder description: "Build a realistic personal monthly budget from someone's income and expenses. Use when asked to make a budget, plan monthly spending, allocate income, or get finances under control. Produces a categorized budget (a 50/30/20-style allocation tuned to their reality), a surplus/shortfall number, and concrete next moves. Educational, not regulated financial advice."

Budget Builder Skill

Most budgets fail because they're aspirational fiction. This skill builds a realistic monthly budget from someone's actual income and spending — categorized, with a clear surplus-or-shortfall number and a couple of specific moves to fix the gap. It's an educational planning aid, not personalized financial advice.

Required Inputs

Ask for these only if they aren't already provided:

• Monthly take-home income (after tax), and whether it's steady or variable.
• Fixed costs — rent/mortgage, utilities, insurance, loan/debt minimums, subscriptions.
• Variable spending — groceries, transport, eating out, fun, shopping (estimates are fine).
• Goals & obligations — emergency fund, debt payoff, saving for something, dependents.

If numbers are rough, work with ranges and say so.

Output Format

Monthly budget — [name/household]

Income (take-home): $X

| Category | Type | Amount | % of income | |---|---|---|---| | Housing | Need | $ | % | | Utilities & bills | Need | $ | % | | Groceries | Need | $ | % | | Transport | Need | $ | % | | Debt minimums | Need | $ | % | | Dining / fun | Want | $ | % | | Subscriptions | Want | $ | % | | Savings / goals | Save | $ | % | | Total | | $ | 100% |

Needs / Wants / Savings split: X% / Y% / Z% — with a one-line read vs. a 50/30/20 guideline (a reference point, not a rule).

Bottom line: surplus of $X (allocate it) or shortfall of $X (must cut/earn).

Top 3 moves — the specific, highest-impact changes (e.g. "renegotiate the $X subscription stack", "cap dining at $Y", "auto-transfer $Z on payday").

Notes — assumptions, and for variable income, budget against a conservative (low) month.

Quality Checks

• [ ] Every dollar is assigned (expenses + savings = income; surplus/shortfall is explicit)
• [ ] Categories are split into needs / wants / savings, with percentages
• [ ] The plan is realistic for their actual spending — not an aspirational fantasy
• [ ] Variable income is handled conservatively (budget the low month)
• [ ] The top moves are specific and quantified, not "spend less"

Anti-Patterns

• [ ] Do not present a budget that doesn't balance to income — name the surplus or shortfall
• [ ] Do not set unrealistic cuts that won't survive week one — anchor to their real numbers
• [ ] Do not ignore irregular costs (annual insurance, holidays) — prorate them monthly
• [ ] Do not give generic advice — every recommendation should reference their figures
• [ ] Do not present this as personalized financial advice — it's an educational plan to adapt

Based On

Personal budgeting practice (zero-based budgeting + the 50/30/20 needs/wants/savings guideline).