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

Annotations already establish readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds genuinely useful behavioral context by revealing the calculation formula (4% rule), the specific inputs required, and the resulting fireNumber magnitude via example. This goes beyond what annotations alone provide.

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?

The description is two tightly packed sentences: the first states purpose and method, the second gives a concrete illustrative example. Every sentence earns its place, and the critical formula is front-loaded before the example.

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 the fully documented schema, the output schema, and annotations, the description is complete. It covers what the tool computes, how it computes it, and demonstrates a realistic call with expected output. No material information an agent needs to invoke this calculator correctly 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 description coverage is 100%, so the parameters are already well documented. The description adds value beyond the schema by showing how the key parameters (expenses, saving, current) combine in a concrete example and clarifying that the result fireNumber 1,200,000 follows from the 4% rule. This is meaningful enrichment over the schema alone.

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 states a specific verb ('Calculate'), a precise resource (financial-independence/FIRE target), the method (4% rule), and a secondary output (years of saving needed). The worked example clarifies the exact input-to-output mapping, and the tool is easily distinguished from financial siblings like compound_interest or cost_of_waiting.

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 clearly implies when to use this tool: whenever an agent needs to compute a FIRE target or time-to-freedom from monthly expenses, savings, and current investments. It does not explicitly name alternatives or exclusion conditions, but the niche formula and example give enough context for correct selection among the siblings.

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