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

The readOnly/idempotent annotations already establish this as a safe, repeatable calculation, so the description's bar is lower. It usefully discloses a non-obvious side output (today's SBA Express rate cap), but says nothing about the amortization formula, rounding, currency, or whether the rate cap is always returned.

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?

Two compact sentences, front-loaded with the primary computation. The second sentence is a slight non sequitur relative to the main purpose but each sentence does carry information.

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?

With no output schema, the description does name both return values (monthly payment and total interest) and mentions an extra rate-cap value. What remains missing (payment frequency is only implied by 'monthly', no formula or rounding detail) is minor for a three-number calculator.

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 100%, so percent-vs-decimal rate, years and dollar amount are already documented. The description adds nothing beyond the schema about the three parameters, so the baseline of 3 applies.

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?

States a specific computation (level monthly payment and total interest for a fully amortizing loan) with a clear resource and named outputs. Slightly muddied by the second sentence, which adds a rate-cap lookup that overlaps with the sibling get_max_rates_today, so the tool's boundary with that sibling is not clean.

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?

Usage is implied: you call it when you need a payment estimate. There is no explicit statement of when to prefer get_max_rates_today or get_program_terms instead, and no mention that the rate must be supplied by the caller rather than fetched.

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