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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely non-obvious behavioral detail no annotation carries: mortgage math uses Canadian semi-annual compounding, and the cap rate is benchmarked against typical local yields. It stops short of 5 because it never mentions the down-payment warnings the schema alludes to, nor any failure/validation behavior.

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 sentences, front-loaded with the domain and the metric list, with the mortgage convention as a trailing caveat. No filler and no restatement of the tool name. Slightly dense as a comma run, but every clause carries 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?

For a 9-parameter calculator with no output schema, listing the returned metrics plus the compounding convention covers most of what an agent needs to call it and trust the result. The gap is that warning behavior (propertyType is 'used for down payment warnings') and the interpretation of the benchmark comparison are never surfaced in the description.

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 every one of the nine parameters (including the city enum used for benchmarking, and annualOperatingExpenses explicitly excluding mortgage) is already documented in the schema. The description adds only the semi-annual-compounding convention, which is a computation note rather than parameter-level meaning. Baseline 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?

The description names the specific analysis domain (Canadian rental property analysis) and enumerates the exact metrics produced: cap rate, NOI, gross rent multiplier, expense ratio, cash flow, cash-on-cash return. That is far more concrete than the name 'cap_rate' alone. It stops short of 5 because it never explicitly distinguishes itself from the mortgage-oriented siblings (mortgage_payment, mortgage_affordability), leaving the agent to infer the boundary.

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 gives no guidance on when to use this tool versus the eleven siblings, and no prerequisites are stated. An agent must infer that 'Cap Rate & Rental Property Calculator' is chosen over mortgage_payment when full rental-property underwriting is wanted. There are no exclusions and no explicit when-to-use clause.

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