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

No annotations are provided, so the description carries the full burden of explaining behavior. It discloses nothing: no input requirements, no calculation type, no return shape, and no side-effect or error behavior.

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 short, but this is under-specification rather than conciseness. The sentence 'Mortgage Calc: Mortgage Calc' contains zero informational content and could have been omitted entirely.

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 tool has six string parameters, no output schema, and no annotations, yet the description provides no context about which parameters are meaningful, whether any are required, how the calculation works, or what the result is. This is completely inadequate for an agent to invoke the tool correctly.

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?

The tool description adds no parameter semantics, but schema description coverage is 100%, which sets a baseline of 3 per the rubric. However, the schema descriptions are formulaic ('Apr to process', 'Rate to process') and add little real meaning beyond the parameter names.

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 'Mortgage Calc: Mortgage Calc' merely repeats the tool name and title; it is a tautology and contains no actionable statement of what the tool does. It gives no verb or resource description and does not distinguish the tool from closely named siblings such as x402-mortgage-payment or x402-loan-payment.

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?

There is no guidance about when to use this tool versus alternatives. It never mentions that it computes mortgage payments or identifies which inputs are needed, and it does not route the agent away from sibling mortgage/loan tools.

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