units.fx_triangulate

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

Annotations already declare readOnly/idempotent/closed-world, so the bar is lower, and the description still adds real behavior: rounding happens exactly once at the target currency's scale, intermediate amounts are not rounded, and the default mode is HALF_EVEN. That is exactly the kind of precision an agent needs to predict output.

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?

Three dense sentences with the formula and return value front-loaded, followed by rate direction semantics and rounding. No filler, though the Korean phrasing packs multiple clauses per sentence.

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?

An output schema exists, so return values need not be re-explained, and the description covers the non-obvious rounding contract. Only minor gaps remain (currency code format, amount sign handling) for a simple arithmetic 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 0%, so the description must carry the load. It defines rate1's direction (from_ccy to via_ccy), rate2's direction (via_ccy to to_ccy), their positivity, and the rounding default, but says nothing about amount formatting, currency code conventions, or the allowed rounding values beyond the default.

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 precise operation: a triangular FX conversion through an intermediate currency (amount * rate1 * rate2), returning amount and currency. The 'via_ccy' framing distinguishes it from the direct-conversion sibling units.fx_convert, though that sibling is never named explicitly.

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?

Usage is implied by the mechanics: you need two rates chained through a via currency. There is no explicit statement of when to prefer this over units.fx_convert, nor any prerequisite or exclusion guidance.

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