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

Annotations already establish the safe, closed-world, read-only profile, so the bar is lower. Because there is no output schema, the description usefully carries the return semantics (target, gap, months-to-close) and implicitly discloses the model: a fixed monthly contribution with no interest or inflation compounding. It does not state edge behavior for zero monthly contribution, which keeps it from a 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?

A single compact clause chain with no filler, and the primary output (the target itself) is front-loaded ahead of the derived gap and timeline values. Nothing could be removed without losing meaning.

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 four-parameter, two-required pure calculator with no output schema, the description covers what the tool returns and how inputs combine. The remaining gap is behavioral edge cases (e.g., monthly = 0 meaning the gap never closes) rather than core information.

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 baseline is 3, but the description adds real meaning by binding each parameter to its role in the formula: expenses times months yields the target, saved determines the gap, and monthly determines the time to close. That is more than the schema's one-line field labels provide.

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 exact resource (emergency fund target) and the three quantities computed: target amount, gap versus savings, and months to close the gap. It is specific and unambiguous, but it never differentiates itself from the many other finance calculators in the sibling list (savings_growth, budget_50_30_20, compound_interest), 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 prerequisites, and no mention of alternatives such as savings_growth for non-emergency savings projections. The topic implies its use case, but nothing in the text routes an agent between this and its siblings.

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