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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds real behavioral value beyond that: the external data source (cap-rate-benchmarks.json), the Tier 2 fallback for unknown ZIPs, the 3% closing assumption for cash-on-cash, and the caveat that bands are estimated survey ranges rather than fresh comps.

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 core computation is front-loaded in the first sentence and the qualifying behaviors follow in a logical order. Four dense sentences stay on topic, though the closing caveat about bands is slightly tangential for a tool-selection description.

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 surface key result semantics (benchmark band comparison, fallback tier, cash-on-cash methodology). Still, for a 10-parameter calculator with 20% schema coverage and multiple undocumented financial inputs, the parameter-level picture is incomplete.

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 only 20% across 10 parameters, so the description bears most of the burden. It clarifies the ZIP param (tier selection only) and the financed path, but leaves interest_pct, loan_term_yrs, down_payment_pct, op_expenses_annual, annual_gross_rent, and property_type essentially undefined beyond their names.

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?

It states a specific verb and resource — a cap rate calculator — and defines the exact computation (NOI divided by purchase price) plus its benchmark comparison. This formula clearly separates it from sibling calculators like calculate_gross_yield or calculate_cash_flow without needing to open their schemas.

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 description explains downstream behavior (unknown ZIPs fall back to the file's Tier 2 band; financed deals use the page's 3% closing estimate), which implies how the tool behaves. However, it never says when to reach for this tool versus alternatives such as calculate_gross_yield or calculate_dscr, leaving selection to inference.

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