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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that: the precise computation model, and the conditional behavior that omitting targetDscr leaves max loan empty. It does not discuss rounding, units, or error conditions.

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?

Five tight sentences, front-loaded with purpose and then the formulas; each sentence adds defining information with little waste. It is dense rather than bloated, though the run-on NOI sentence could be broken up for readability.

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 10-parameter, no-output-schema calculator, the description supplies the outputs (DSCR, max loan), the derivation of each, and the conditional parameter behavior, which is enough to invoke it correctly. The main residual gap is that loanAmount and the rate/term inputs are not explicitly mapped into the debt-service or max-loan computation.

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 only 10%, so the description carries most of the burden, and it largely does: monthlyRent (rent times 12), vacancyPct (1 minus vacancy), taxesAnnual, insuranceAnnual, hoaAnnual, otherAnnual, and targetDscr (omit it and max loan stays empty). ratePct and termYears are only implied via 'fully amortizing payment', and loanAmount's role is never stated, leaving a small but real gap.

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 opens with a specific verb+resource ('DSCR calculator') and goes further by spelling out the exact NOI, debt-service, and max-loan formulas, making its scope unmistakable against siblings like calculate_cap_rate or calculate_amortization. It stops short of naming or contrasting those siblings explicitly, so it is clear but not sibling-differentiating.

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 only implied by the formulas and the note that targetDscr is optional and that '1.25 is not assumed' – useful signal that max loan is only returned when a target is supplied. There is no explicit when-to-use guidance and no routing to alternative calculators such as calculate_amortization or calculate_cap_rate.

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