Currency Rates (ECB)

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds that the return value is a map of currency code to name, providing useful context beyond annotations. No contradictions.

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 brief and front-loaded with the main verb. However, the second and third sentences are somewhat redundant (both mention code and name), and there is a minor typo with double period.

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 burden of explaining return values. It states the map structure and content, and for a zero-parameter read-only tool this is sufficient.

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?

The tool has zero parameters, so the baseline is 4. The description accurately describes the fixed output without needing parameter clarification.

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 clearly states the tool lists all supported currencies, providing ISO 4217 codes and English names. This distinct purpose is obvious against sibling tools that focus on rates.

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 states what the tool does but offers no explicit comparison to get_historical_rates or get_latest_rates. Usage context is implied by the tool name and sibling set, but no when-to-use vs alternatives guidance is provided.

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

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

Annotations already declare the tool as read-only/non-destructive. The description adds valuable context about returning rates on or nearest before the given date, but omits details on response format or error cases. It does not contradict annotations.

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 short and front-loaded with a clear action, but the final 'Returns:' line is redundant with the preceding sentence and includes a typo, so it doesn't fully earn its place.

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 read-only tool, it covers key behavioral details like the 'nearest before' logic and clearly states the return type. However, without an output schema, a bit more detail on the structure of returned rates would be beneficial, though not critical.

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 all parameters are already documented. The tool description does not add further meaning to the parameters beyond what the schema provides, warranting the baseline score of 3.

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 clearly states the tool fetches exchange rates for a past date, specifies ECB reference rates, and highlights the 'nearest before' behavior, distinguishing it from tools like get_latest_rates.

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 context for when to use this tool is clear (for past dates), but it does not explicitly mention alternatives or exclusionary guidance. Still, the purpose is unambiguous enough to imply correct usage.

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

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds value by specifying the data source (ECB), the default base currency, and the return format (keyed by currency code). This goes beyond a simple 'get' and provides useful behavioral context without contradicting annotations.

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 short and gets to the point quickly. However, it has redundancy ('Returns the most recent...' and later 'Returns: Latest...') and a minor punctuation issue (double period). It's still efficient and front-loaded, but loses a point for not being as polished as it could be.

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 read-only tool with high schema coverage and no output schema, the description is largely complete: it covers purpose, source, default behavior, and return format. It doesn't elaborate on symbols usage or potential error responses, but those are adequately covered by the schema and the tool's simplicity. A 5 would require explicit mention of exactly when to use this over alternatives.

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 the baseline is 3. The description repeats that base defaults to EUR, which is already in the schema, but does not add new semantic detail for either parameter. It does not explain symbols further or clarify edge cases, so it neither compensates nor subtracts.

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 clearly states the tool fetches the latest exchange rates, specifically the most recent ECB reference rates. This distinguishes it from sibling tools like get_historical_rates (historical data) and get_currencies (currency metadata), making the purpose unambiguous.

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 implies when to use this tool: for current/latest rates. While it doesn't explicitly contrast with historical rates or list alternative tools, the context is clear and the sibling name 'get_historical_rates' reinforces the distinction. It lacks an explicit exclusion statement, preventing a 5.

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