SmartFin

Project savings growth

smartfin_project_savings_growth

Read-onlyIdempotent

Future balance of savings or an investment growing at a fixed yearly rate, with optional monthly contributions and a chosen compounding frequency. Returns the balance, total paid in and interest earned. Use for forward-looking "how much will I have" questions at an assumed rate. Do not use for what a real stock did in the past (use smartfin_calculate_investment_return). A fixed rate is an assumption, not a forecast.

Input Schema

TableJSON Schema

Name	Required	Description
`years`	Yes	Number of years
`principal`	Yes	Starting amount in dollars
`annual_rate_pct`	Yes	Assumed yearly rate in %, e.g. 7
`compounds_per_year`	No	1 yearly, 2 twice a year, 4 quarterly, 12 monthly, 365 daily. Default 12
`monthly_contribution`	No	Added each month, in dollars. Default 0

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.

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

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuine behavioral context beyond them: the fields returned (balance, total paid in, interest earned) and the important caveat that the fixed rate is an assumption, not a forecast, setting expectations on output interpretation.

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?

Three tight sentences: definition first, then usage routing, then the assumption caveat last. No filler, and the most decision-relevant information (scope and the sibling alternative) is front-loaded.

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?

With an output schema, full parameter coverage, and clear annotations, the description needs only to cover scope, routing, and interpretive caveats — all of which it does. An agent has everything required to select and call the 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 description coverage is 100%, so all five parameters (including the compounding enum and monthly contribution) are already documented in the schema. The description only restates 'monthly contributions' and 'compounding frequency' without adding syntax or defaults, so the baseline 3 applies.

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 and resource — computes a future balance for savings/investment at a fixed yearly rate — and even names what it returns. It explicitly distinguishes itself from smartfin_calculate_investment_return, so an agent can route without opening either schema.

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 explicit when-to-use ('forward-looking how much will I have at an assumed rate') and an explicit when-not-to-use with the alternative named ('what a real stock did in the past — use smartfin_calculate_investment_return'). 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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