SmartFin

Present value of a future amount

smartfin_calculate_present_value

Read-onlyIdempotent

What an amount due in the future is worth today at a fixed yearly discount rate, and the discount between the two (PV = FV / (1 + r/n)^(n x t)). Use for questions about the value today of money received later, at a discount rate the user supplies. Do not use to pick a discount rate (the tool has none of its own), for several payments over time, or for a market price: it discounts one amount at one fixed rate. For growth going forward use smartfin_calculate_future_value.

Input Schema

TableJSON Schema

Name	Required	Description
`years`	Yes	Years until the amount is due; a part of a year is a decimal
`currency`	No	Currency symbol for the amounts in the summary only; amounts are never converted. The link opens the page in US dollars, and how_to says to pick the currency there. Default USD
`future_value`	Yes	Amount due later, in the currency chosen
`annual_rate_pct`	Yes	Yearly discount rate in %, above -100, e.g. 6
`compounding_frequency`	Yes	Times a year the rate compounds: 1 annually, 2 semiannually, 4 quarterly, 12 monthly, 52 weekly, 365 daily

Output Schema

TableJSON Schema

Name	Required	Description
`cite`	Yes	How to credit this result
`data`	Yes
`next`	Yes	Suggested follow-up calls
`links`	Yes
`how_to`	Yes	Steps for the user to see or redo this on smartfin.fyi
`source`	Yes
`summary`	Yes	Plain-language result the assistant can quote

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 18, 2026

addedInput schema / properties / currency

Added value: +{
+  "description": "Currency symbol for the amounts in the summary only; amounts are never converted. The link opens the page in US dollars, and how_to says to pick the currency there. Default USD",
+  "enum": [
+    "USD",
+    "EUR",
+    "GBP",
+    "CHF",
+    "AUD",
+    "CAD",
+    "SGD",
+    "HKD",
+    "INR",
+    "JPY"
+  ],
+  "type": "string"
+}

changedInput schema / properties / future_value / description

Previous value: -"Amount due later, in dollars"New value: +"Amount due later, in the currency chosen"

AddedOct 13, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds real scope context beyond them: the tool holds no rate of its own and discounts exactly one amount at one fixed rate, which tells the agent this is a bounded single computation rather than a solver. It does not discuss precision or rounding, but the output schema is present.

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?

Front-loaded with the definition and formula, then when-to-use, then exclusions, then the alternative. Three tight sentences with no redundant restatement of the name or title, and every clause carries routing or scope information.

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?

For a read-only single-formula calculator with a full output schema and 100% parameter documentation, the description supplies everything an agent lacks: the mathematical relationship, the scope limit (one amount, one fixed rate), and the sibling to use for the opposite direction. Nothing needed to select or call it correctly is 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 future_value, annual_rate_pct, compounding_frequency, years and currency in detail. The description only echoes that the discount rate is user-supplied, adding no format or constraint detail beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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 (discount to present value) and resource (a single future amount), and even gives the formula PV = FV / (1 + r/n)^(n x t). It is clearly separable from smartfin_calculate_future_value, which it explicitly names as the inverse operation.

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?

Gives an explicit when-to-use (questions about the value today of money received later, at a user-supplied rate), three explicit when-not cases (picking a rate, multiple payments, market price), and names the alternative sibling for forward growth. 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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