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

With no annotations provided, the description carries the behavioral burden alert and does disclose one important runtime trait: latest CDN mortgage rates are used for defaults, implying live or externally sourced rates. It does not disclose assumptions like PMI applicability thresholds or the default loan term, so behavioral transparency is partial.

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 three terse sentences with no filler: it front-loads the output composition, then adds the key default-rate behavior. Every clause earns its place and nothing needs to be cut.

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?

The lack of an output schema is partially offset by naming the full PITI breakdown, so the agent knows what the tool returns. However, important completion details are missing, such as what default loan term is used when loanTermYears is omitted and how PMI is derived when it is not a schema parameter.

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?

Schema description coverage is 100%, so all six parameters are already documented in the schema. The description adds only high-level output categories and the CDN default-rate behavior, but it does not explain parameter relationships such as down payment percentage affecting PMI or the units expected.

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 clearly identifies a specific calculation: monthly mortgage payment with a detailed P&I plus property tax, insurance, and PMI output, framed as a full PITI breakdown. This differentiates it from sibling calculators like calculate_car_loan or calculate_compound_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?

The intended context is implied by "mortgage" and the note about CDN rates, but the description does not explicitly say when to prefer this tool over alternatives or when not to use it. There is clear context, but usage guidance is left to inference rather than stated.

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