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

No annotations are present, so the description carries the burden. It discloses a specific behavioral trait ('Points lose if you sell early') and the planned hold period as an input, but it does not explain underlying assumptions (e.g., fixed-rate mortgage, compounding, upfront cost calculation). This provides some transparency but misses important details about how the tool computes results.

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 sentences and front-loaded with the title, but the first phrase repeats the tool name/title ('Mortgage Discount Points Break-Even Calculator —'). It efficiently conveys the core purpose, outputs, and a caveat without fluff, though the introductory redundancy slightly reduces conciseness.

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?

Given the tool has 6 required parameters, no output schema, no annotations, and no parameter descriptions, the description is too sparse. It does not define units (e.g., annualRatePct is a percentage), the meaning of 'points,' or the relationship between 'points' and 'rateReductionPerPoint.' An agent would need to infer too much to invoke the tool correctly, especially with no output schema to clarify return values.

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 0%, and the description only references 'hold period' and 'points' implicitly. It fails to explain critical parameters like 'rateReductionPerPoint' or how 'points' are denominated (percentage vs. number). The parameter names in the schema are somewhat self-explanatory, but the description does not compensate for the lack of schema-level documentation, leaving ambiguity for correct invocation.

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 states the tool's purpose: to find out if buying mortgage discount points is worth it, with specific outputs (break-even month and net gain). The verb 'Find out' and the resource 'mortgage discount points' make it specific, and it distinguishes itself from sibling calculators like generic break_even_calculator or mortgage_refinance_calculator by focusing narrowly on discount points.

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 description implies usage context: use when considering buying mortgage discount points, and it highlights a key caveat ('Points lose if you sell early'). It doesn't explicitly name alternative tools or state when not to use it, but the specialized focus provides clear situational context for the agent.

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