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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral context by disclosing which formulas are applied and that the comfortable range is capped at 36% total debt. It does not say what changes when monthly_debts is omitted, which is the main behavioral 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?

A single dense sentence with no filler, and the primary input/output relationship is front-loaded. The rule list is long but each item is substantive rather than padding.

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 two-parameter calculator with no output schema and annotations covering safety, the description supplies the key missing context (the rules that produce the answer). It stops short of explaining behavior when the optional debts parameter is absent or what the returned figures look like.

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 50%: monthly_debts is documented in the schema, monthly_gross_income is not. The description reinforces the income input and the '36% total debt' cap implies how monthly_debts is used, but it adds no format, units, or optionality details beyond the schema.

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 a specific computed output (affordable rent) from a specific input (gross monthly income), and enumerates the rules applied, which distinguishes it from the mere ratio tool rent_to_income. It does not explicitly say how it differs from sibling rent_to_income, so it falls 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?

There is no when-to-use guidance, no statement of when to prefer this over rent_to_income or debt_to_income, and no prerequisites. Usage must be inferred from the name and the list of rules.

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