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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new context: results are neutral scenario math rather than an approval, it operates only on explicit non-identifying numbers, and it performs no lookups from chats, files, accounts, documents, or the web. The openWorldHint=false annotation partially overlaps the last point, keeping this just below 5.

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 no-approval idea is stated twice in near-identical terms ('not an approval or underwriting decision' and 'no approval, underwriting, or suitability decisions'), and 'It computes the payment itself, so it needs those loan terms' is filler. The scope statement is front-loaded and the disclaimers are placed last, which helps.

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?

An output schema exists, so return values need not be explained. For a 12-parameter compute tool with nested housing and tolerances objects, the description conveys the domain, the conceptual inputs, and the strong scope boundaries. The only gap is that optional overrides like floorRate and bufferRate are never surfaced in prose.

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 75%, so the schema carries most parameter meaning, including detailed rate-as-decimal formatting and defaults. The description names only principal, contract rate, amortization, and income, leaving floorRate, bufferRate, tolerances, housing, otherMonthlyDebts, and straightSwitchExempt entirely to the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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: it computes the B-20 qualifying rate, qualifying payment, and resulting GDS/TDS from named inputs. An agent can tell this is a qualification math tool rather than a debt-service or LTV tool. It never names a sibling to differentiate against, so it stops short of a 5.

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 through the input prerequisites ('from a principal, contract rate, amortization, and income') and what it deliberately is not (no approval or underwriting decision). But it gives no explicit when-to-use versus calculate_debt_service, calculate_ltv, or compare_mortgage_scenarios, so routing must be inferred from the name.

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