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

No annotations are provided, so the description carries full burden. It transparently discloses that rates are indicative, not for settlement/trading, and explains the 'source' and 'market_session' fields as freshness indicators. It also clarifies update frequency and fallback behavior. This is strong behavioral transparency.

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 a single, information-dense paragraph. It is front-loaded with the primary purpose, then provides necessary details. It is concise but could benefit from slight restructuring for readability, but no sentence is wasted.

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 the tool's complexity (real-time vs fallback, multiple data sources) and the absence of annotations, the description provides thorough context. It explains freshness, fallback scenarios, and what fields to inspect. An output schema exists, so return value details are not required. It is nearly complete for an agent to invoke effectively.

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 0%, so the description must compensate. It mentions the 'date' parameter for historical rates, but does not detail the format or constraints for 'base' and 'quote' (e.g., currency codes). The description adds context on the response's 'source' and 'market_session' that relate to parameters implicitly, but not enough to fully compensate for the lack of schema descriptions.

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 gets exchange rates for a currency pair, with optional historical dates. It distinguishes itself from siblings like convert, get_range, and list_currencies by focusing on rate retrieval, and it specifies its data source and limitations.

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 explicitly explains when rates are real-time vs fallback, and when to expect official daily data (market closures, low liquidity). It does not explicitly name alternative tools for conversions or ranges, but it gives clear context on typical usage scenarios and behavior.

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