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

Annotations already indicate read-only and idempotent behavior. The description adds the 'No advice' disclaimer and explains the computational outputs (gap and years to reach), providing useful context beyond what annotations convey. It does not discuss error handling or edge cases, but the safety profile is well-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?

The description is a single, well-structured sentence that captures the tool's purpose, key inputs, default, and outputs, followed by a concise disclaimer. Every word earns its place, with no redundancy or excessive detail.

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?

With a complete schema, annotations, and an output schema present, the description adequately covers the tool's purpose and core outputs. It could mention limitations or assumptions beyond the default 4% rule, but the provided information is sufficient for an agent to use the tool correctly in most scenarios.

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 descriptions cover 100% of parameters, providing a solid baseline. The description adds meaning by synthesizing how parameters interact: 'gap from today' implies comparison with currentNestEgg, and 'years to reach it' uses annualContribution and growth. This goes beyond individual property descriptions to clarify the calculation flow.

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 calculates a FIRE target nest egg from annual spend and safe withdrawal rate, plus the gap from today and years to reach it. This specific verb+resource with default rate distinguishes it from sibling calculators like barista-fire and coast-fire.

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 provides clear context for when to use the tool (standard FIRE calculation) by specifying inputs and outputs. It does not explicitly exclude alternatives or mention sibling tools, but the unique combination of nest egg, gap, and years-to-target gives enough guidance for an agent to select it over similar calculators.

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