SmartFin

Inflation impact over time

smartfin_calculate_inflation_impact

Read-onlyIdempotent

What an amount will be worth in today's money after years of inflation at a fixed yearly rate, and what something costing that amount today will cost then. Use for questions about buying power or future prices at an assumed inflation rate. Do not use for historical CPI lookups: this uses one fixed rate, not official index data.

Input Schema

Name	Required	Description
`years`	Yes	Number of years
`amount`	Yes	Amount in the currency chosen
`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
`annual_inflation_pct`	Yes	Yearly inflation rate in %, e.g. 3

Output 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.

Changed5 schema fields changedNov 1, 2026
- changedInput schema / properties / amount / maximum
```
Previous value: -1000000000000New value: +100000000
```
- changedInput schema / properties / amount / minimum
```
Previous value: -0New value: +1
```
- changedInput schema / properties / annual_inflation_pct / maximum
```
Previous value: -1000New value: +100
```
- changedInput schema / properties / annual_inflation_pct / minimum
```
Previous value: --99New value: +-20
```
- changedInput schema / properties / years / maximum
```
Previous value: -200New value: +40
```

Changed2 schema fields changedOct 18, 2026

changedInput schema / properties / amount / description

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

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"
+}

Changed1 schema field changedSep 29, 2026

addedOutput schema / properties / links / properties / page

Added value: +{
+  "description": "SmartFin's page for this stock, when it has one",
+  "type": "string"
+}

First observedSep 29, 2026

TDQS

A4/5.0

Behavior4/5

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

The annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely useful interpretation context beyond that: the model assumes a single fixed yearly rate rather than observed index data, which tells the agent the output is a hypothetical projection, not historical fact.

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?

Two sentences, both earning their place: the first defines the computation in both directions, the second handles usage and the key exclusion. The trigger and the caveat are front-loaded with no filler.

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 full schema coverage, full annotation coverage, and an output schema covering return values, the description only needs to establish what is computed and under what assumption — which it does. Nothing critical is missing, though a brief note on how the two outputs are labeled would remove the last ambiguity.

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% and the schema already explains years bounds, amount bounds, the inflation range, and the currency enum's display-only semantics. The description adds no parameter-level meaning beyond that, so the baseline 3 applies.

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 states precisely what is computed: the present-day value of an amount after years of fixed-rate inflation, and the future cost of today's amount — a real purchasing-power calculation. It is unmistakable from compounding siblings like calculate_future_value, though it does not name a sibling tool by name to differentiate further.

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

Usage Guidelines4/5

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

"Use for questions about buying power or future prices at an assumed inflation rate" gives a clear trigger, and "Do not use for historical CPI lookups: this uses one fixed rate, not official index data" gives an explicit exclusion with the reason. It stops short of naming the alternative tool an agent should pick instead, so it is not a full 5.

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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