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

With no annotations, the description carries the full behavioral burden. It helpfully discloses the return payload (monthly payment, total interest, total paid, balance schedule), but it omits calculation assumptions, the effect of the locale parameter, and the format of the balance schedule.

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 two sentences, front-loaded with the tool's purpose, and structured as inputs and returns. Every phrase earns its place 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?

For a simple calculator with no annotations, no output schema, and 0% schema description coverage, the description is adequate but incomplete. It explains the main return values but leaves gaps around the locale parameter, defaults, and the meaning of the balance schedule.

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 description coverage is 0%, so the description must compensate. It explains three of four parameters and adds a useful unit for rate ('annual %'), but it completely omits the locale parameter and gives no default values or further meaning for principal and months.

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 states a specific verb and resource: 'Compute a loan.' It also lists the expected inputs and outputs, making the tool's purpose clear. However, it does not differentiate this tool from related siblings such as compound-interest, so it stops short of a 5.

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 gives no explicit when-to-use or when-not-to-use guidance, and it does not mention alternatives such as compound-interest. Usage is only inferable from the name and purpose statement.

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