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

Annotations already declare readOnlyHint and idempotentHint, and the description adds the behavioral formula: the portfolio funds the remainder after part-time income at the safe withdrawal rate. This goes beyond the annotations by explaining the calculation logic, though edge cases are not covered.

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, well-front-loaded sentence that defines the tool's purpose without redundant words. Every part of the description earns its place.

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?

Given a simple three-parameter calculator with an output schema, the description sufficiently conveys the core calculation and result. It does not explicitly formulaize (annualSpend - partTimeIncome) / withdrawalRatePct, but the concept is clear enough for a simple tool.

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 adds meaning by clarifying that annualSpend and partTimeIncome are combined (the remainder is funded) and that withdrawalRatePct is the divisor, which goes beyond the schema's simple 'Yearly spending' descriptions.

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 clearly states the tool computes the nest egg needed when part-time income covers part of spending, defining the calculation concept. It is distinct from generic fire-number and coast-fire siblings, though it lacks an explicit verb like 'calculate'.

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?

The description implies usage when part-time income partially covers spending, but it does not explicitly mention when not to use it or compare it with alternatives like coast-fire or fire-number. The condition is present but not framed as guidance.

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