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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds the after-tax basis and the three destination buckets, but says nothing about rounding, precision, or what happens with zero/negative income. With annotations doing the heavy lifting, this is adequate rather than rich.

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 efficient sentence that front-loads the method and the input basis, then names the output split. No filler.

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 one-parameter pure calculator with no output schema, the description supplies enough: the income basis and the three result categories. It could go one step further by noting that three amounts are returned or how debt paydown is treated, but nothing essential 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?

Only one parameter and schema coverage is 100%, so the schema already documents 'income' as monthly after-tax income. The description restates the same qualifier ('after-tax income') without adding units, currency, or range constraints, so baseline 3 applies.

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 (split), a specific resource (monthly after-tax income), a named rule (50/30/20) and the exact output buckets (needs, wants, savings/debt paydown). An agent can tell this apart from neighbors like savings_growth or emergency_fund without opening a schema.

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 only implied: 'monthly after-tax income' signals the input basis, but the description never states when to use this versus savings_growth, emergency_fund, or a plain percentage split. For a set of independent calculators, implicit context is tolerable but there is no explicit guidance or exclusion.

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