API Tool Calls

Retirement Income Calculator

retirement_drawdown

Read-onlyIdempotent

Arithmetic on entered numbers only: level end-of-period withdrawal, total withdrawn and complete period table from a balance, fixed entered nominal annual return and term. Monthly, quarterly or annual periods; nearest-cent half-up rounding; final withdrawal clears residue. Rates are entered, never fetched.

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,
      "balance": 100,
      "frequency": "annually",
      "annualReturnPercent": 10
    },
    "name": "retirement_drawdown"
  }
}

Input Schema

Name	Required	Description
`years`	Yes	Whole years; at most 360 monthly, 120 quarterly or 30 annual rows.
`balance`	Yes	Starting balance in USD, at most two decimal places.
`frequency`	Yes	Withdrawal timing: 12 monthly, 4 quarterly or 1 annual end-of-period withdrawal per year.
`annualReturnPercent`	Yes	Entered fixed nominal annual return percentage; at most six decimal places, divided by periods per year.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 5, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld=false and non-destructive, so the safety profile is covered. The description goes beyond them with genuinely useful behavior: nearest-cent half-up rounding, the final withdrawal clearing residual balance, and the guarantee that rates are entered rather than fetched.

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?

Two dense sentences, front-loaded with the core computation and then the period/rounding details, with no filler. It is information-rich but slightly packed, which costs a little readability.

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?

With a full output schema, the return values need not be re-explained, and annotations cover safety. The description supplies the calculation convention (level end-of-period, half-up rounding, residue clearing) that an agent needs to invoke it correctly, leaving only sibling-routing guidance missing.

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 the schema already documents all four parameters with ranges, enum values and semantics. The description adds only marginal meaning ('monthly, quarterly or annual periods', 'end-of-period withdrawal', 'final withdrawal clears residue') beyond what the schema states, so the baseline 3 is 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 resource (retirement drawdown) and precisely enumerates outputs: level end-of-period withdrawal, total withdrawn, and a complete period table from a balance, return and term. It also draws a boundary ('arithmetic on entered numbers only... rates are entered, never fetched') that separates it from rate-fetching or market-data tools among the many calculator siblings.

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

Usage Guidelines3/5

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

Usage is implied by the clear domain (level retirement withdrawals) and the input-source note ('rates are entered, never fetched'), which tells the agent this is a pure offline calculator. However, it never states when to prefer this over the closely related loan_schedule or compound_interest_calculator siblings, nor any exclusions or prerequisites.

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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