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apetta

Vibe Math MCP

by apetta

Financial Calculations

financial_calcs
Read-onlyIdempotent

Solve for present value, future value, payment, interest rate, IRR, or NPV in time value of money calculations. Input known variables to compute unknown financial metrics for loans, investments, annuities, and bonds.

Instructions

Time Value of Money (TVM) calculations: solve for PV, FV, PMT, rate, IRR, or NPV.

The TVM equation has 5 variables - know 4, solve for the 5th: PV = Present Value (lump sum now) FV = Future Value (lump sum at maturity) PMT = Payment (regular periodic cash flow) N = Number of periods I/Y = Interest rate per period

Sign convention: negative = cash out (you pay), positive = cash in (you receive)

Examples:

ZERO-COUPON BOND: PV of £1000 in 10 years at 5% calculation="pv", rate=0.05, periods=10, future_value=1000 Result: £613.91

COUPON BOND: PV of £30 annual coupons + £1000 face value at 5% yield calculation="pv", rate=0.05, periods=10, payment=30, future_value=1000 Result: £845.57

RETIREMENT SAVINGS: FV with £500/month for 30 years at 7% calculation="fv", rate=0.07/12, periods=360, payment=-500, present_value=0 Result: £566,764

MORTGAGE PAYMENT: Monthly payment on £200k loan, 30 years, 4% APR calculation="pmt", rate=0.04/12, periods=360, present_value=-200000, future_value=0 Result: £954.83

INTEREST RATE: What rate grows £613.81 to £1000 in 10 years? calculation="rate", periods=10, present_value=-613.81, future_value=1000 Result: 0.05 (5%)

GROWING ANNUITY: Salary stream with 3.5% raises, discounted at 12% calculation="pv", rate=0.12, periods=25, payment=-45000, growth_rate=0.035 Result: £402,586

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
contextNoOptional annotation to label this calculation (e.g., 'Bond A PV', 'Q2 revenue'). Appears in results for easy identification.
output_modeNoOutput format: full (default), compact, minimal, value, or final. See batch_execute tool for details.full
calculationYesWhat to solve for: pv, fv, pmt, rate, irr, or npv
rateNoInterest/discount rate per period (e.g., 0.05 for 5% annual)
periodsNoNumber of compounding periods
paymentNoRegular periodic payment (negative=pay out, positive=receive)
present_valueNoSingle lump sum at time 0 (negative=pay, positive=receive)
future_valueNoSingle lump sum at maturity (negative=owe, positive=receive)
cash_flowsNoSeries of cash flows for IRR/NPV (e.g., [-100, 30, 30, 130])
whenNoPayment timing: 'end' (ordinary) or 'begin' (annuity due)end
growth_rateNoPayment growth rate per period (0.0 for level annuity)

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and idempotentHint, so the tool's safety profile is known. The description adds value by explaining the sign convention (negative=cash out, positive=cash in) and demonstrating the behavior through examples. No contradictions with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured: it starts with a summary, then explains the TVM equation, sign convention, and provides numerous clear examples. Every section serves a purpose, and the length is appropriate for the complexity of the tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's high complexity (11 parameters, 1 required) and the existence of an output schema, the description covers all necessary aspects: all calculation types, sign convention, and multiple scenarios including growing annuity. It leaves no gaps for the agent to understand how to invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Input schema covers 100% of parameters with descriptions, but the description enriches meaning by explaining the TVM variable relationships and providing examples that show how parameters like rate, periods, payment, etc., work together. The sign convention adds crucial semantic context beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Time Value of Money (TVM) calculations: solve for PV, FV, PMT, rate, IRR, or NPV.' It specifies the resource (TVM calculations) and the action (solve for), distinguishing it from sibling tools like compound_interest or perpetuity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear guidance on when to use this tool through the TVM equation explanation and sign convention. It includes multiple examples covering common financial scenarios. However, it does not explicitly mention alternatives or when not to use this tool, like for simple interest calculations which might be better handled by compound_interest.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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