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tvm-fund

by io.finance-tools.tvm

calculate_present_value

Read-onlyIdempotent

Calculate the present value of a single future amount: what a future lump sum is worth today discounted at a given rate over a given number of periods. Formula: PV = FV / (1 + r)^n. WHEN TO USE: Use to discount a single known future cash flow back to today (e.g. a future exit value, a balloon payment, or a single future receipt). WHEN NOT TO USE: Do NOT use for multiple cash-flow streams (use calculate_npv) or for perpetual/annuity streams (use the perpetuity or annuity tools). BEHAVIOUR: pure deterministic calculation — no side effects, no network or storage access; idempotent and non-destructive; identical inputs always produce identical outputs. Division by zero, non-finite inputs, or mathematically undefined combinations return an explicit error instead of a number. RETURNS: JSON object { present_value: number (currency), inputs }. PARAMETERS: future_value (required): Future amount in currency units, e.g. 250000. May be negative for a future payment. rate (required): Discount rate as a decimal, e.g. 0.10 = 10% per period (never pass percentage points). Rate and periods must share frequency. periods (required): Number of discounting periods, e.g. 5. Must be >= 0.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
rateYesDiscount rate as a decimal, e.g. 0.10 = 10% per period (never pass percentage points). Rate and periods must share frequency.
periodsYesNumber of discounting periods, e.g. 5. Must be >= 0.
future_valueYesFuture amount in currency units, e.g. 250000. May be negative for a future payment.

TDQS

A4.6/5.0
Behavior5/5

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

Annotations already mark the tool as readOnly and idempotent, and the description adds valuable detail beyond that: pure deterministic calculation, no side effects or network/storage access, and explicit error behavior for division by zero, non-finite inputs, and undefined combinations. This enriches the agent's understanding of what will happen at runtime.

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?

The description is well-structured with clear labeled sections and front-loaded purpose. However, the PARAMETERS section duplicates the schema's property descriptions nearly verbatim, adding length without introducing new information. Overall it is organized and each section has a clear role.

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?

There is no output schema, so the RETURNS section appropriately describes the response shape (present_value and inputs). The description also covers error behavior, period/rate frequency alignment, and all required parameters. Nothing critical is missing for an agent to call this tool correctly.

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 coverage is 100% — the input schema already documents all three parameters with the same examples and constraints. The description repeats the parameter information rather than adding meaning beyond the schema, though the formula context and the emphasis on not passing percentage points do reinforce correct usage.

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 states exactly what the tool does — discounts a single future lump sum — and provides the formula. It explicitly distinguishes itself from related siblings like calculate_annuity_present_value and calculate_perpetuity_value, so an agent can select it correctly without opening schemas.

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?

Dedicated WHEN TO USE and WHEN NOT TO USE sections name specific alternatives (calculate_npv, annuity, perpetuity tools) and the exact conditions under which each should be chosen instead. This is explicit routing guidance, leaving nothing 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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TDQS

A4.6/5.0
Disambiguation5/5

Each tool targets a mathematically distinct calculation (single-sum PV/FV, annuity, perpetuity, payback, fund multiples). The descriptions include explicit 'WHEN TO USE' and 'WHEN NOT TO USE' sections with cross-references, making it unambiguous which tool applies to which scenario.

Naming Consistency5/5

All tool names follow the exact pattern verb_noun with the consistent 'calculate_' prefix (e.g., calculate_present_value, calculate_payback_period). The naming convention is uniform across the entire set.

Tool Count5/5

11 tools is well within the ideal range for a focused domain. Each tool addresses a distinct calculation relevant to time-value-of-money and fund performance, with no redundant entries.

Completeness3/5

The set covers many core calculations but is missing NPV and IRR, which are explicitly referenced as the recommended tools in several descriptions (e.g., payback periods, TVPI). This creates a notable gap that could lead agents to follow cross-references to non-existent tools.

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