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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds meaningful behavioral context beyond those: 'Estimates only — not financial advice,' the statePension overlay is 'not subtracted from the FIRE numbers,' and optional savings/coast parameters change the output to include years until each country unlocks. This helps avoid misinterpretation of results.

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 one long, dense sentence, but it is front-loaded with the core purpose and then enumerates outputs. There is no filler, though splitting into a few sentences would improve readability.

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 output schema exists, the description thoroughly covers the key input relationship and enumerates the important output categories: tiers, FIRE numbers, nomad-visa eligibility, local currency, SWR sensitivity, savings/coast effects, and statePension caveats. The only lightly documented parameter is 'source,' but the enum values are fairly self-explanatory and the required portfolio parameter is well covered.

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 83%, and the schema already explains most parameters including accepted fraction/percent forms for swr and return. The description adds only aggregate mentions of portfolio/SWR and savings/coast mode, without detailing each parameter, so it neither substantially improves nor hurts parameter understanding.

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 a specific verb-plus-resource purpose: given a portfolio and SWR, return all countries where passive income supports specified FIRE lifestyle tiers. It is distinct from sibling tools by its geo-arbitrage FIRE focus, though it does not explicitly name or differentiate itself from a sibling such as find_nomad_visas.

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: when a user wants country-level FIRE feasibility based on a portfolio and withdrawal rate. It does not state exclusions or name alternative tools, but the FIRE-specific framing makes the intended use case fairly unambiguous.

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