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

The description provides rich behavioral context far beyond the annotations. It explains the rounding logic ('Rounding remainders land on the final payment'), the specific licensing requirement, and the critical error handling format (returning a structured error object instead of raising a protocol exception).

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 definition is logically structured, flowing from the main purpose to an explicit example, and then concluding with technical constraints and error handling. Every sentence adds critical, non-redundant 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?

Given that this is a calculation and scheduling tool, the definition is exceptionally complete. It covers the math, the business constraints (license), the operational safety (read-only/idempotent), and the specific error reporting structure.

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 input schema provides 100% coverage, the description significantly enhances the semantics by providing a concrete, fully worked example of inputs and expected outputs, which helps an agent visualize the calculation.

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 immediately states the core function: 'Split a total into an installment schedule with optional deposit.' It distinguishes itself from sibling tools like invoice_total by focusing on the scheduled payment creation rather than just total calculation.

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 usage guidelines are perfectly clear, defining the correct use case ('one total is paid across scheduled dates') while providing a clear exclusion ('Not for partial-period adjustments (proration)').

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