Calculate mortgage PITI

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

Annotations already carry readOnlyHint and idempotentHint, so the bar is lower. The description adds meaningful behavioral details: no network call, 20% default down payment, automatic PMI when LTV > 80% and pmi_rate is provided, and the exact choice between annual tax and tax-rate inputs. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is dense but efficient, with every sentence earning its place. It front-loads the core purpose, then immediately covers defaults and conditional parameters in a compact, readable structure.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 10-parameter tool with no output schema, the description covers the output format, defaults, and conditional inputs well. It falls slightly short on edge cases: what happens if neither property tax parameter is supplied, if both down_payment and down_payment_percent are supplied, or if pmi_rate is omitted. These are minor but not explicitly addressed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With only 40% schema description coverage, the description compensates strongly: it explains mutual exclusivity of down_payment/down_payment_percent, the 20% default, the property_tax_annual vs property_tax_rate choice, and the automatic PMI condition. It also clarifies that HOA and insurance are part of the breakdown, adding meaning beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Local-only mortgage payment calculator. Returns a full PITI breakdown...' It clearly specifies the computed outputs and distinguishes this from sibling tools like homes_calculate_affordability by emphasizing PITI and total interest.

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

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

It provides clear operational context with 'Local-only' and 'No network call,' and gives explicit either/or rules for down_payment and property tax inputs, plus PMI conditions. It does not explicitly name a sibling alternative such as homes_calculate_affordability, so exclusion of alternatives is implied rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.