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

The description adds substantial context beyond the readOnlyHint annotation: it discloses the data source (FRED), update frequency (daily), pricing (x402 SLA), failure behavior (503 when upstream unavailable), and the data_source field. This exceeds the baseline expectations for a read-only tool.

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 dense but information-rich. It front-loads the main content and includes important operational details. Minor redundancy exists around the 503 and SLA mention, but every sentence adds value.

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?

The tool has no output schema, so the description partially compensates by listing the data fields (pairs, changes, data_source). However, it does not specify the exact response format or units. For a simple tool with one optional parameter, the coverage is nearly complete.

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 schema has one optional parameter (base_currency) with enum values, but schema description coverage is 0%. The description does not explain what base_currency does or how it affects the results, leaving the agent to infer from the enum values alone. This is a significant gap.

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 specifies the resource: live major currency pair benchmarks, listing concrete pairs and indices (USD/EUR, USD/JPY, etc.), source (FRED), and update frequency. It distinguishes from sibling benchmark tools by focusing on FX 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 implies this tool is for FX rate benchmarks, but it does not explicitly state when to use it versus alternatives. No exclusions or alternative tool references are provided, so the guidance is only implied.

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