Google Fx Rate

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), but the description adds real operational context: Google rate-limiting, the blocked-result failure mode, and why it is more layout-resilient than finance pages. It stops short of describing pagination or latency, but the added context is substantive.

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?

Short and front-loaded: purpose, return shape, differentiation, and the rate-limit caveat each occupy about one sentence. Only the final rate-limit sentence is slightly tangential to selection, but it earns its place as an operational warning.

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 detailed, and the routing guidance is complete. However, with six undocumented parameters and no schema descriptions, an agent lacks guidance on locale/engine options, which keeps this from being fully complete.

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 0% across six parameters, so the description carries the full burden. The example '1 USD to IDR' loosely implies base/quote/amount, but gl, hl, and engine are never explained and no value formats or defaults are clarified beyond the schema itself.

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?

States a specific verb and resource ('live rate from the SERP converter widget') with a concrete example ('1 USD to IDR') and names the output field fx_rate. It also distinguishes itself from the sibling google_kurs_bi, so an agent can route without opening either schema.

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?

Explicitly says when to use it ('quick rates') and when not to ('for official BI rates use google_kurs_bi'), plus a fallback path when results are blocked (wait or switch to an RSS-based tool). Both the alternative and the exclusions are stated outright.

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