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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: it discloses the three results produced (ratio, max loan, required rent) and warns that the rate is caller-supplied rather than an offered rate, which prevents a real misuse. It stops short of describing output shape or rounding.

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 tight sentences with the core definition front-loaded and no filler. Minor ambiguity in the trailing 'and the rent needed', which does not say what rent is needed for (presumably to hit the target DSCR), costing a point.

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 burden of explaining returns, and it does list the three computed values. What is missing is only the shape of the response and how target/ltv defaults flow into the sizing outputs, which is a modest gap for an 8-parameter read-only 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 coverage is 100%, so the schema already documents every parameter including defaults for hoa, ltv and target. The description's formula ('monthly rent divided by principal, interest, taxes, insurance and HOA') adds conceptual meaning by showing how taxes/insurance/hoa combine into the denominator, but it does not explain ltv or target semantics beyond the schema. 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?

States a specific verb and resource — computes the debt service coverage ratio on a rental — and goes further by naming the two derived outputs (largest supported loan at 1.05x and the rent needed). The sibling tools (compare_lenders, get_lender_terms, match_deal) are clearly different functions, so there is no routing ambiguity.

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: this is a per-property underwriting calculation for a rental. The one explicit guidance sentence ('The rate is whatever you pass; it is not an offered rate') clarifies input provenance rather than when to use the tool. No when-not conditions or alternatives are named, and no prerequisites (e.g. it's a single-property calc, not a comparison) are stated.

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