Convert currency

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

Annotations already cover safety (readOnly, idempotent) and open-world behavior. The description goes further by disclosing the data source, archival frequency (once per working day), 12-hour caching, keyless/free access, and coverage limits — operational facts annotations cannot express.

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?

Four well-bounded sentences that front-load the core action, then layer source, use case, cost/latency, and coverage. Every sentence adds a fact an agent needs; slightly dense but no filler.

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?

For a simple 3-param read-only tool with no output schema, the description covers what it does, data provenance, freshness, limits, and cost. The only mild gap is that it doesn't describe the response shape (converted amount, rate), though annotations render that low-stakes.

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%; every parameter (amount, from, to) is fully documented with types, patterns, and examples. The description adds the currency-coverage caveat (unsupported codes like PKR, AED) which is genuinely useful beyond the schema, but does not clarify parameter syntax further. Baseline 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?

Specific verb+resource ('Convert an amount between currencies') with the data source named (ECB reference rates). It is clearly distinguishable from all siblings, none of which deal with currency, and the description preempts confusion by naming supported and unsupported currencies.

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?

Gives clear context ('Good for comparing fares quoted in different currencies') and an explicit negative boundary (currencies the ECB does not publish are unavailable). It does not name an alternative tool for unsupported currencies, but the exclusion is concrete enough to route the agent.

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