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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuine interpretive context beyond that: the 33% rule-of-thumb threshold and the fact that a verdict is returned, which tells the agent how to read the result.

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, then usage, then inputs/returns. Efficient overall, though the input list partly restates the schema and the bundle pointer is slightly tangential.

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 explaining return values isn't required, yet the description still notes the ratio % and verdict. Combined with the threshold heuristic and the related-bundle pointer, an agent has enough to call this correctly; only the alternative-tool routing is missing.

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 baseline is 3. The description still adds meaning by specifying 'monthly rent' and 'monthly gross income' — the gross-vs-net distinction is a real semantic constraint the schema's generic 'Monthly income' does not make.

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 ('Compute the rent-to-income ratio') and frames it as a housing-affordability assessment. This distinguishes it reasonably well from near-neighbors like calculate_debt_to_income, but it never names an alternative, so the differentiation is inferred rather than explicit.

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?

Gives a clear usage context ('Use to assess housing affordability') and a helpful decision rule (keep under 33%). However it offers no when-not guidance and does not point to related or overlapping calculators such as calculate_debt_to_income or calculate_rent_increase_irl, so alternatives are left implicit.

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