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

Annotations already establish read-only and idempotent behavior; the description adds transparency about the calculation method (pricing note-rate payment against net proceeds), which helps the agent understand the formula without contradicting the 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 a single sentence that front-loads the purpose ('Effective APR including upfront fees') and provides the formula in a compact manner with no filler.

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 schema coverage, output schema, and annotations, the description is sufficient to understand the tool's scope; the formula detail covers the behavioral nuance, making it complete for an AI agent.

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?

While the schema fully documents each parameter, the description adds relational semantics by explaining how fees reduce the amount to net proceeds, which clarifies the interplay between amount, fees, and the resulting APR.

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 identifies the tool's function: calculating effective APR that includes upfront fees, and distinguishes it from simpler effective-rate tools by specifying the net proceeds calculation (amount - fees).

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 implies the tool is for loans with upfront fees, but does not explicitly compare to alternatives like effective-rate or state when not to use it, so it earns a 4.

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