calculate_installments

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

The readOnlyHint annotation already covers side-effect transparency. The description adds context about the calculation inputs (promotion, surcharge, fee, interest) but does not explicitly state that no data is modified; however, this is adequately covered by the annotation.

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 concise sentences with no redundancy. It front-loads the core purpose, then details the included factors, and ends with a clear directive. Every sentence adds value.

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 calculation tool with no output schema, the description covers the essential behavior, the mandatory usage rule, and the components of the calculation. It does not mention potential error conditions, but given the readOnly annotation and low complexity, it is sufficiently complete.

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 description gives some context for sku and plan_id (via 'for a SKU under one instalment plan'), but it does not explain the sku format or the quantity parameter beyond the schema's minimal 'Default 1.' With schema coverage at 67%, the description adds limited value for parameter understanding.

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 verb 'calculate' and the specific output ('exact monthly payment') for a given SKU and installment plan. It also sets a strong expectation with 'Never quote instalments without calling this,' making the tool's purpose unambiguous.

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 explicitly instructs when to use the tool ('Never quote instalments without calling this'), which serves as a definitive usage rule. It also lists what the calculation includes (promotion, surcharge, fee, interest), clarifying the scope of the result.

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