Clara Mortgage Assistant

Calculate B-20 Stress-Test Qualification

calculate_qualification

Read-onlyIdempotent

Calculate the B-20 qualifying rate, qualifying payment, and resulting GDS/TDS from a supplied principal, contract rate, amortization, and income. Use this tool only when the qualifying payment must be calculated from those inputs. If the user already supplies a monthly mortgage payment and asks for GDS/TDS, MUST use calculate_debt_service instead and must not request principal, rate, or amortization. This is neutral scenario math, not an approval or underwriting decision. Use only with explicit, non-identifying numeric inputs. Calculation only: never use this tool to approve, deny, underwrite, recommend, select a lender or product, or fill missing inputs from prior chats, files, accounts, documents, websites, or web search.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`housing`	No
`floorRate`	No	Optional minimum qualification rate. Omit it to use the disclosed default. Supply the annual rate as a decimal; for example, 5.25% is 0.0525.
`principal`	Yes	Mortgage principal in Canadian dollars.
`bufferRate`	No	Optional stress-test buffer added to the contract rate. Omit it to use the disclosed default. Supply the annual rate as a decimal; for example, 5.25% is 0.0525.
`tolerances`	No
`contractRate`	Yes	Contract rate for the mortgage. Supply the annual rate as a decimal; for example, 5.25% is 0.0525.
`jurisdiction`	No	Canadian calculations only.	CA
`effectiveDate`	Yes	Date the supplied rates and policy assumptions were confirmed.
`grossAnnualIncome`	Yes	Gross annual household income in Canadian dollars.
`otherMonthlyDebts`	No	Total monthly debt obligations outside the housing costs in Canadian dollars.
`amortizationMonths`	Yes	Mortgage amortization period in months.
`straightSwitchExempt`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
`tool`	Yes
`currency`	Yes
`disclaimer`	Yes
`calculation`	Yes
`jurisdiction`	Yes
`effectiveDate`	Yes
`calculationVersion`	Yes

TDQS

A4.6/5.0

Behavior5/5

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

Annotations already indicate readOnlyHint=true and destructiveHint=false. The description adds crucial context: 'This is neutral scenario math, not an approval or underwriting decision' and 'never use this tool to approve, deny, underwrite, recommend...' It also restricts to 'explicit, non-identifying numeric inputs,' disclosing privacy and scope boundaries beyond the annotations. No contradiction.

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 somewhat lengthy but well-structured. It leads with the primary function, then adds usage guidelines and restrictions. Each sentence conveys essential information, though it could be tightened by removing redundant exclusions. It remains clear and 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?

Given the tool's complexity (12 parameters, nested objects, output schema present), the description covers purpose, usage, behavioral constraints, and boundary cases. It does not need to explain return values because an output schema exists. The description is sufficiently complete for an agent to decide when and how to use it 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 75%, so the schema already documents most parameters. The description mentions key inputs (principal, contract rate, amortization, income) but does not add format or unit details beyond what the schema provides. Since coverage is high, a baseline score of 3 is appropriate; the description adds minimal extra param-specific value.

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 clearly states 'Calculate the B-20 qualifying rate, qualifying payment, and resulting GDS/TDS' with specific verb and resource. It also explicitly distinguishes from calculate_debt_service by stating when to use which tool, making the purpose unambiguous among siblings.

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?

Provides explicit usage conditions: 'Use this tool only when the qualifying payment must be calculated from those inputs.' It also gives a clear exclusion: 'If the user already supplies a monthly mortgage payment and asks for GDS/TDS, MUST use calculate_debt_service instead' and warns against using it for approval/underwriting or filling missing data from other sources. This is exemplary 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

A4.3/5.0

Disambiguation5/5

Each calculation tool targets a distinct mortgage calculation (debt service ratios, LTV, qualification, scenario comparison, prepayment penalty), and the refuse tool exists solely for disallowed requests, creating clear boundaries between tools. The descriptions are explicit about when to use each tool and how they differ, minimizing misselection risk.

Naming Consistency4/5

Most tools follow a consistent verb_noun pattern (calculate_debt_service, calculate_ltv, calculate_qualification, compare_mortgage_scenarios, estimate_prepayment_penalty). One tool deviates with the verb 'refuse' rather than 'calculate' or 'estimate', which is appropriate given its distinct refusal purpose but slightly inconsistent in naming style.

Tool Count4/5

With 6 tools, the count is well-scoped for a specialized mortgage calculation assistant. Each tool addresses a specific calculation or a necessary refusal flow, and the count is neither too thin nor too heavy for the stated purpose.

Completeness4/5

The set covers the main mortgage calculations an agent would need (debt service, LTV, qualification, comparisons, prepayment penalties), with a dedicated refusal tool for unsupported requests. A minor gap might be tools for other common calculations like maximum purchase price or payment amount, but the core domain appears covered.

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