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

Annotations already declare readOnlyHint and idempotentHint, covering safety traits. The description adds the comparative nature of the calculation ('versus the baseline schedule'), but doesn't disclose assumptions like interest compounding or payment timing. This adds some value beyond annotations but is not richly detailed.

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 a single sentence that is direct and free of unnecessary words. It front-loads the outcome ('Time and interest saved') clearly, making it easy to grasp.

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 9 parameters and several related sibling tools, the description is minimal. It doesn't mention the two modes ('term' vs 'payment') or the optional extra payments, though these are covered in the schema. The presence of an output schema reduces the need to describe returns, but a bit more context on the baseline schedule and assumptions would make it more complete for an agent to invoke 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?

Schema coverage is 100%, so all parameters have descriptions. The tool description adds no parameter-specific information; however, the schema itself is comprehensive, so a baseline score of 3 is appropriate.

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 calculates time and interest saved by making fixed extra monthly payments, using the specific verb 'saved' and resource 'loan'. While it doesn't explicitly distinguish it from similar sibling tools like 'biweekly-payoff' or 'credit-card-payoff', the phrase 'fixed extra amount every month' implies the differentiation, making it clear but not fully explicit.

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 provides no guidance on when to use this tool compared to alternatives such as biweekly-payoff or debt-payoff. There is no mention of preferred scenarios, exclusions, or references to sibling tools. The usage context is only implied by the tool's purpose.

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