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

With no annotations, the description carries the behavioral disclosure burden. It usefully discloses that missing inputs fall back to documented defaults, signaling that all parameters are optional. It does not describe the return format, error behavior, or explicitly state there are no side effects, though the computational nature is evident.

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, front-loaded with the action, and organizes the outputs in a compact list. The redundant phrase 'calculator calculator' is awkward but does not obscure meaning or significantly hurt clarity.

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 calculator with seven fully documented optional parameters, the input side is adequately covered. However, since there is no output schema, the description should more explicitly describe how results are returned; the listed output names help but do not fully compensate for that missing structure.

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 schema already describes all seven parameters at 100% coverage, so the baseline is 3. The description adds the default-fallback behavior, but this mostly mirrors the defaults already present in the schema and adds no additional insight into how the parameters interact or should be chosen.

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 uses a specific imperative ('Run') with the calculator resource and lists four concrete outputs: all-in interest rate, monthly payment capital/interest, interest-only payment, and arrangement fee. This clearly differentiates it from sibling tools like calculator_describe, which likely describes the calculator rather than executing it.

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 is implied that the tool should be used when mortgage calculation outputs are needed, and the listed outputs clarify the intended scenario. However, there is no explicit statement of when to prefer it over siblings or any conditions/preconditions, leaving routing mostly to inference.

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