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

Annotations already declare it is read-only, closed-world and non-destructive. The description adds useful context beyond that: that the 55% figure is the lender's published ceiling rather than an approval, and that the balance compounds semi-annually with no payments. It doesn't say which rate drives the projection or what the output looks like, so a 3 fits.

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?

A single dense sentence with the key caveat (ceiling not approval) front-loaded and the projection horizons at the end. Every clause carries information, though the em-dash nesting makes it slightly harder to scan.

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?

With no output schema, the description carries the burden of explaining what comes back, and it only sketches the outputs (max amount, balance vs equity at four horizons). Given that all five parameters are fully documented in the schema, the definition is adequate but not complete.

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%, including the rateTerm enum and the 55% cap on amountTaken, so the schema already does the work. The description reinforces the ceiling concept but adds no syntax or format 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?

Names a specific computation on a specific resource: the theoretical maximum (55% of value) and the compounding balance versus home equity at 5/10/15/20 year horizons. It doesn't explicitly distinguish itself from the nearby siblings heloc_second_mortgage or mortgage_amortization, but the '55+' and 'no payments' framing makes the concept recognizable on its own.

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 '55+' eligibility and 'CHIP-style' framing imply the context in which to use it, but nothing states when to pick this over heloc_second_mortgage or a standard amortization tool, and there are no exclusions or prerequisites beyond the age requirement.

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