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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds genuine value by disclosing the computation and the NOI derivation fallback, plus a note about the interactive version. It does not state output formatting (percent vs. decimal), which is the remaining gap.

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 short sentences, front-loaded with the core computation and followed by input guidance and the sibling routing. The external URL is the only arguably extraneous element.

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 carries the return-value burden and does enumerate the three results, which is enough to call the tool correctly. Minor gap: it never says what units the cap rate is expressed in or how the results are shaped.

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 every parameter is already documented, including the NOI fallback rule. The description's either/or phrasing of noi_usd versus gross/expenses restates schema semantics rather than extending them. Baseline 3 is appropriate.

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?

Names the specific metric and its formula (net operating income / property value), plus the two secondary outputs (gross rent multiplier, price per unit). It also explicitly distinguishes itself from the sibling cash_on_cash, so an agent can route without opening either schema.

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?

"Give noi_usd directly or gross income and operating expenses" gives explicit input paths, and "Use cash_on_cash when financing matters" names an alternative with the selecting condition. It does not address other valuation siblings (irr, moic, startup_valuation), but the key fork is covered.

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