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

Annotations already establish readOnly and idempotent, and the description adds real behavioral context: sourced regulator URLs with as_of dates, no invented fees/FX/coverage, and a not_in_catalog fallback for unknown scenarios. That failure-mode disclosure is the valuable part; the cost/rate-limit profile ('free, no key') is a minor add.

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?

Front-loaded verb and scope in the first clause, then return shape, then country coverage and safety guarantees. Four sentences, no filler, though 'Free, no key' is the least load-bearing line.

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?

No output schema exists, so the description carries the return contract, and it does: per-country scheme info, regulator URLs, as_of dates, and a documented not_in_catalog outcome. It stops short of stating what the agent should do on not_in_catalog or whether the two countries may be identical.

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 100%, so both required country codes and the topic enum are already documented. The description only restates that results are returned for from_country and to_country, adding no formatting, case, or same-country guidance beyond the schema.

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: answering cross-border deposit-protection questions with sourced scheme info for a from_country/to_country pair. The cross-border, deposit-insurance framing plus the explicit country list implicitly separates it from siblings like scheme_lookup and money_fact, but no sibling is named.

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?

Implies when to use it (cross-border money questions about deposit protection for non-residents) and bounds the domain to US/UK/CA/AU/NZ. However, it never tells the agent when to prefer scheme_lookup or money_fact instead, leaving the routing to inference.

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