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

The description adds transparency beyond the annotations by specifying the standard amortization formula and warning that all amounts share the same but unspecified currency. These are behavioral details not captured by the read-only/idempotent annotations.

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 short sentences, with the primary purpose in the first sentence and key behavioral notes following. Every sentence adds value without repetition or padding.

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 description is sufficient for this simple calculator: it covers the calculation type, formula, and currency caveat, while the output schema and annotations fill in the remaining structural details. Nothing essential is missing.

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 input schema already documents all three parameters, so the description doesn't need to repeat them. However, it adds the semantic note that principal and computed amounts use the same currency, which clarifies how to interpret the numeric values.

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 opens with a specific verb 'Compute' and names the exact financial outputs (monthly payment, total interest, total cost) and the loan type (fixed-rate amortizing). This clearly distinguishes it from the many other calculator siblings and states the tool's core function.

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 clearly defines the use case: fixed-rate amortizing loans, which implies it is not for other loan types. However, it does not mention any alternative tools or explicitly state when not to use it, so it stops short of full usage guidance.

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