TrueCalci

Compound wealth growth

compound_wealth

Read-onlyIdempotent

Standard precision: this calculator uses ordinary floating-point arithmetic, keeps no dated table of official rates, and has not yet passed our full reference-test suite. Simulate long-term compound interest growth for retirement portfolios, 401(k)s, Roth IRAs, UK ISAs, or European ETF savings plans (Sparplan) with recurring monthly deposits.

Behavior: Deterministic, idempotent calculation with zero external side effects. Applies discrete compound interest formula with periodic annuity deposits: Future Value = P*(1 + r/n)^(nt) + PMT(((1 + r/n)^(n*t) - 1)/(r/n)). Returns final accumulated balance, total principal contributed, total compound interest earned, and annual wealth progression milestone table.

Usage Guidelines: Use for multi-year personal wealth projection and retirement nest-egg simulations. Do not use for Indian mutual fund monthly SIPs with annual step-up; use sip_investment instead.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "annualRatePercent": "<annualRatePercent>",
      "tenureYears": "<tenureYears>"
    },
    "name": "compound_wealth"
  }
}

Input Schema

Name	Required	Description
`principal`	No	Initial lump-sum deposit or starting balance in currency units. Must be non-negative and at most 1,000,000,000,000,000.
`tenureYears`	Yes	Investment horizon in years (e.g. 10, 20, 30). Must be an integer from 1 to 200.
`monthlyDeposit`	No	Recurring monthly contribution added to the account. Must be non-negative and at most 1,000,000,000,000,000.
`annualRatePercent`	Yes	Expected annualized investment return rate percentage (e.g. 8 for 8%). Must be positive.
`compoundFrequency`	No	Number of compounding periods per year, a whole number from 1 to 365 (1 for annual, 4 for quarterly, 12 for monthly).

Output Schema

Name	Required	Description	Default
`principal`	No
`futureValue`	No
`totalInterest`	No
`totalDeposited`	No
`yearlySchedule`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed12 schema fields changedOct 18, 2026

changedInput schema / properties / compoundFrequency / description

Previous value: -"Number of compounding periods per year (1 for annual, 4 for quarterly, 12 for monthly)."New value: +"Number of compounding periods per year, a whole number from 1 to 365 (1 for annual, 4 for quarterly, 12 for monthly)."

addedInput schema / properties / compoundFrequency / maximum
```
Added value: +365
```
addedInput schema / properties / compoundFrequency / minimum
```
Added value: +1
```

changedInput schema / properties / monthlyDeposit / description

Previous value: -"Recurring monthly contribution added to the account. Must be non-negative."New value: +"Recurring monthly contribution added to the account. Must be non-negative and at most 1,000,000,000,000,000."

addedInput schema / properties / monthlyDeposit / maximum
```
Added value: +1000000000000000
```
addedInput schema / properties / monthlyDeposit / minimum
```
Added value: +0
```

changedInput schema / properties / principal / description

Previous value: -"Initial lump-sum deposit or starting balance in currency units. Must be non-negative."New value: +"Initial lump-sum deposit or starting balance in currency units. Must be non-negative and at most 1,000,000,000,000,000."

addedInput schema / properties / principal / maximum
```
Added value: +1000000000000000
```
addedInput schema / properties / principal / minimum
```
Added value: +0
```

changedInput schema / properties / tenureYears / description

Previous value: -"Investment horizon in years (e.g. 10, 20, 30). Must be an integer >= 1."New value: +"Investment horizon in years (e.g. 10, 20, 30). Must be an integer from 1 to 200."

addedInput schema / properties / tenureYears / maximum
```
Added value: +200
```
addedInput schema / properties / tenureYears / minimum
```
Added value: +1
```

Changed1 schema field changedSep 27, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "futureValue": {
+      "type": [
+        "string",
+        "number",
+        "null"
+      ]
+    },
+    "principal": {
+      "type": [
+        "string",
+        "number",
+        "null"
+      ]
+    },
+    "totalDeposited": {
+      "type": [
+        "string",
+        "number",
+        "null"
+      ]
+    },
+    "totalInterest": {
+      "type": [
+        "string",
+        "number",
+        "null"
+      ]
+    },
+    "yearlySchedule": {
+      "type": [
+        "array",
+        "null"
+      ]
+    }
+  },
+  "type": "object"
+}

Changed2 schema fields changedSep 24, 2026
- removedInput schema / properties / annualRatePercent / default
```
Removed value: -8
```
- removedInput schema / properties / tenureYears / default
```
Removed value: -15
```

Changed5 schema fields changedSep 5, 2026

changedInput schema / properties / annualRatePercent / description

Previous value: -"Expected annual return in %"New value: +"Expected annualized investment return rate percentage (e.g. 8 for 8%). Must be positive."

changedInput schema / properties / compoundFrequency / description

Previous value: -"Compounding frequency per year (12 = monthly)"New value: +"Number of compounding periods per year (1 for annual, 4 for quarterly, 12 for monthly)."

changedInput schema / properties / monthlyDeposit / description

Previous value: -"Monthly recurring contribution"New value: +"Recurring monthly contribution added to the account. Must be non-negative."

changedInput schema / properties / principal / description

Previous value: -"Initial principal deposit"New value: +"Initial lump-sum deposit or starting balance in currency units. Must be non-negative."

changedInput schema / properties / tenureYears / description

Previous value: -"Duration in years"New value: +"Investment horizon in years (e.g. 10, 20, 30). Must be an integer >= 1."

First observedSep 5, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive/no-open-world, so 'deterministic, idempotent, zero side effects' mostly restates structured data. The description earns credit for the precision disclaimer (floating-point math, no dated official rate table, has not passed the full reference-test suite) and the explicit formula, which are genuine reliability disclosures an agent cannot get from annotations.

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

Conciseness4/5

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

Long but labeled and front-loaded (precision caveat, behavior, usage guidelines), with no filler. The opening disclaimer sentence is slightly dense, but every sentence carries information useful for correct invocation.

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?

An output schema exists, yet the description still summarizes the return shape (final balance, total principal, total interest, milestone table), and it covers scope, math, and routing to the alternative. Nothing an agent needs to call this correctly is missing.

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?

Schema coverage is 100%, so baseline is 3. The description goes beyond the schema by giving the actual annuity formula that maps principal, rate, compounding frequency and monthly deposit onto the result, which clarifies how compoundFrequency and monthlyDeposit interact rather than just what they are.

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?

States a specific verb and resource: 'Simulate long-term compound interest growth for retirement portfolios, 401(k)s, Roth IRAs, UK ISAs, or European ETF savings plans.' It also names the sibling it is not (sip_investment), so an agent can distinguish it without opening a schema.

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

Usage Guidelines5/5

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

Explicit when-to-use ('multi-year personal wealth projection and retirement nest-egg simulations') and when-not-to-use ('Indian mutual fund monthly SIPs with annual step-up'), with the concrete alternative sip_investment named. Nothing is left to inference.

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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