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

The description adds useful behavioral detail beyond the all-false annotations: the last period absorbs rounding, the schedule lands exactly on the balloon or zero, and loans_report depends on it. However, one of these annotations is readOnlyHint=false while the description says 'Build,' which leaves it ambiguous whether this tool mutates persistent state or merely computes and returns a schedule. That side-effect ambiguity is not resolved.

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?

Three compact sentences with zero waste. The core action and output fields are front-loaded, followed by the rounding guarantee and the sibling relationship. Every sentence earns its place.

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?

There is no output schema, so the description carries the burden of describing the return content, and it does: per-period columns plus total interest, with a rounding guarantee. It does not explicitly state the response shape or how filters like year/from_period affect rows, but the schema covers those and the tool is simple enough that an agent can invoke it correctly.

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 coverage is 100%, so the baseline is 3; the input schema fully documents loan, year, limit, and from_period. The description adds the concept of 'period' and 'total interest' but does not explain any parameter behavior beyond what the schema already states.

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 uses a specific verb ('Build') and resource ('one loan's schedule') and enumerates the exact output fields: opening balance, payment, interest, principal, closing, and total interest. It also distinguishes itself from the sibling loans_report by noting 'loans_report totals it,' so an agent can tell this tool produces the per-loan schedule rather than an aggregate report.

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 phrase 'one loan's schedule' clearly scopes this tool to a single loan, and the closing note that loans_report totals it hints at the alternative for aggregate reporting. It does not explicitly state when not to use this tool, but the single-loan scope and sibling relationship provide sufficient decision context.

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