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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is known. The description adds context about the return values (target, projected balance, coasting status, shortfall) and the deterministic nature of the projection, which goes beyond the annotations without contradicting them.

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 front-loads the concept and then lists the return values. Every word earns its place, with no unnecessary fluff or repetition.

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?

The description is complete for this tool: it explains the concept, lists return values, and is supplemented by a full schema, output schema, and clear annotations. There is no hidden complexity or missing information that would leave an AI agent uncertain about invocation.

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%, with each parameter having a clear description (e.g., 'Amount invested today', 'Expected annual growth in percent'). The tool description adds minimal parameter-specific meaning, but the schema already carries the load, so the baseline score of 3 is appropriate.

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's function: evaluating whether a current nest egg left untouched reaches the FIRE target at retirement. It specifies the resource ('current nest egg') and the action ('whether it coasts'), and distinguishes it from sibling FIRE calculators like fire-number or barista-fire by the unique coast FIRE concept.

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 the usage context (checking coast FIRE status) but does not explicitly state when to choose this over alternatives like barista-fire or fire-number. There is no mention of exclusions or alternative tools, so the guidance is implied rather than explicit.

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