API Tool Calls

Compound Interest Calculator

compound_interest_calculator

Read-onlyIdempotent

Calculate compound or simple interest, balance, total contributed, interest earned, modeled APY and yearly balances from principal, nominal rate, term and deposit timing.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "years": 2,
      "principal": 1000,
      "annualRate": 10,
      "contribution": 100,
      "compoundingPerYear": 1,
      "contributionTiming": "end",
      "contributionFrequency": "yearly"
    },
    "name": "compound_interest_calculator"
  }
}

Input Schema

Name	Required	Description
`mode`	No	Interest calculation; default compound
`years`	Yes	Term in years; a fractional tail earns modeled interest
`principal`	Yes	Initial principal (USD; at most two decimal places)
`annualRate`	Yes	Nominal annual rate / APR (%)
`contribution`	No	Recurring deposit per complete monthly/yearly period; default 0; simple mode requires 0 (USD; at most two decimal places)
`compoundingPerYear`	No	Equal compounding periods per year, default 12
`contributionTiming`	No	Deposit at start or end of each complete period; default end
`contributionFrequency`	No	Deposit interval, default monthly; fractional intervals have no deposit

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 4, 2026

TDQS

B3.2/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered without description help. The description adds only the enumeration of computed outputs, with no extra behavioral context (e.g., rounding, currency, precision behavior) beyond what annotations supply.

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?

A single front-loaded sentence with no filler; the long output enumeration makes it slightly list-heavy, but every clause maps to something the tool actually produces.

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

Completeness4/5

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

An output schema exists, so return values need no explanation, and the schema carries all parameter detail. The description is complete enough for an agent to call correctly; only the absent sibling-routing and mode caveats keep it from being fully self-sufficient.

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

Parameters3/5

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

Schema description coverage is 100%, so all eight parameters are already documented in the schema with defaults, ranges and units. The description only paraphrases the top-level inputs (principal, nominal rate, term, deposit timing) and adds no syntax or edge-case detail beyond the schema, making baseline 3 appropriate.

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

Purpose4/5

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

The description names a specific verb (Calculate) and resource (compound or simple interest) and enumerates the concrete outputs (balance, total contributed, interest earned, APY, yearly balances) plus the driving inputs. It clearly separates the two modes, though it does not differentiate itself from numerically adjacent siblings such as loan_schedule, roi, or inflation_calculator.

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

Usage Guidelines2/5

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

No when-to-use or when-not-to-use guidance is given. The agent is not told how this differs from loan_schedule or roi, nor any preconditions such as the constraint that simple mode forbids contributions (though that lives in the schema).

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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