BetterOff

PITI mortgage calculator

calc_mortgage

Read-onlyIdempotent

Read-only educational calculator. Calculates monthly PITI mortgage payment, total interest, total cost, and builds amortization schedule from home price, down payment, rate, and term. Returns a result from caller-supplied public inputs without changing page or account state, accessing BetterOff customer data, or providing personalized financial advice.

Input Schema

TableJSON Schema

Name	Required	Description
`annualTax`	No	Annual property tax
`homePrice`	No	Home price
`monthlyHOA`	No	Monthly HOA — Monthly homeowners association fee, if applicable.
`closingCosts`	No	Closing costs — Upfront lender and transaction costs, excluding the down payment.
`annualRatePct`	No	Interest rate (%) — Fixed annual note rate before fees.
`loanTermYears`	No	Loan term (years)
`downPaymentPct`	No	Down payment (%) — Percentage of home price paid upfront as equity.
`annualInsurance`	No	Annual insurance
`annualPmiRatePct`	No	Annual PMI rate (%) — Applies when the down payment is under 20%; use the rate from a loan estimate when available.
`monthlyMaintenance`	No	Monthly maintenance reserve — Optional owner-paid maintenance budget; not part of PITI.
`extraPrincipalMonthly`	No	Extra principal each month — Additional principal payment used to shorten payoff and reduce interest.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

TDQS

A4.5/5.0

Behavior5/5

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

Beyond the readOnly/idempotent/destructive annotations, the description explicitly guarantees no page or account state change, no access to BetterOff customer data, and use of only caller-supplied public inputs. This adds privacy and scope context that the annotations do not convey.

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?

The description is two well-structured sentences: it front-loads the read-only/educational nature, enumerates outputs and input categories, then closes with explicit non-effects. Every clause adds useful information with no filler.

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 all 11 optional parameters fully documented in the schema and an output schema present, the description only needs to orient the agent on selection and behavior, which it does. It covers outputs, input sources, no state change, no customer-data access, and no personalized-advice use.

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% and each parameter has its own helpful description, so the schema carries the parameter documentation burden. The description only summarizes inputs as 'home price, down payment, rate, and term' and does not add per-parameter meaning beyond that.

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 a specific verb and resource: it 'calculates monthly PITI mortgage payment, total interest, total cost, and builds amortization schedule.' This clearly defines what the tool does and distinguishes it from the other calc_* siblings focused on different financial scenarios.

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?

The description provides clear context: it is a 'read-only educational calculator' and explicitly disclaims personalized financial advice, telling the agent when not to use it. It does not name alternative calculators or provide a direct selection rule, so it stops short of the strongest sibling-differentiation guidance.

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

A3.8/5.0

Disambiguation2/5

The 14 calc_* tools are individually distinct, but run_public_calculator and compare_public_scenarios overlap with all of them, making it unclear when to use a specific calculator versus the generic runner. list_public_calculators and search_public_docs also have somewhat fuzzy boundaries.

Naming Consistency5/5

All tool names follow a consistent snake_case verb_noun pattern (calc_*, list_*, get_*, search_*, compare_*, run_*), with no mixed casing or irregular verb styles.

Tool Count3/5

At 22 tools, the set is on the heavy side and falls in the borderline 16–25 range. While most calculators earn their place, the generic run_public_calculator and compare_public_scenarios duplicate functionality already covered by the calc_* tools, inflating the count.

Completeness5/5

The surface covers a broad personal-finance calculator domain plus discovery, contract introspection, running, comparing, docs, pricing, and feature details. For a read-only educational server, there are no obvious gaps or dead ends.

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