fx_spot

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

With no annotations, the description carries full behavioral burden and does so exceptionally: it discloses the 14:15 CET fixing time, TARGET business days, closed-day fallback behavior, and the fact that non-EUR pairs are derived crosses marked with 'derived': true. It even instructs the agent to report that flag.

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 compact and front-loaded: the core rate semantics appear first, followed by essential caveats and a direct instruction. Every sentence earns its place, with no filler or repetition of schema fields.

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 there is no output schema and no annotations, the description covers the essential operational context: source, timing, holiday behavior, cross derivation, and a response field. It does not describe the full response shape or date format, but it is sufficient for correct invocation in most cases.

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%, so the description must compensate. It clearly explains the base/quote relationship and that omitting date gives the latest rate. However, it does not specify the expected date format or further constrain the date parameter beyond the schema's default empty string.

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 precisely defines the tool's purpose: it provides the ECB euro reference rate and states the rate semantics as 'how many quote buy one base.' It also distinguishes itself by clarifying this is a daily fixing, not a traded spot rate, which separates it from the sibling fx_period_rate and generic spot tools.

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 gives clear context: omit date for latest, and closed days return the last publication before them. It does not explicitly name alternatives or state when not to use this tool versus fx_period_rate, but the fixing-vs-traded-rate distinction implies the appropriate use context.

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