get_supported_currencies

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

Annotations already provide readOnlyHint=true and openWorldHint=true, indicating this is a safe read operation with dynamic data. The description adds value by specifying the output format ('list of three-letter currency codes'), which isn't covered by annotations. However, it doesn't disclose additional behavioral traits like rate limits, caching, or data freshness, which could be useful context.

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, efficient sentence that directly states the tool's function without any fluff. It's front-loaded with the core action and resource, making it easy for an agent to parse quickly. Every word earns 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?

Given the tool's low complexity (0 parameters, simple read operation) and good annotations, the description is mostly complete. It explains the output format, which is crucial since there's no output schema. However, it could improve by mentioning if the list is static or updates dynamically, aligning with the openWorldHint annotation.

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 0 parameters, and schema description coverage is 100%, so there's no need for parameter details in the description. The description appropriately focuses on the output, which is helpful since there's no output schema. This meets the baseline of 4 for zero-parameter tools.

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's purpose with a specific verb ('Returns') and resource ('list of three-letter currency codes for the supported currencies'). It distinguishes itself from siblings by focusing on currency codes rather than conversion or historical rates, though it doesn't explicitly name alternatives.

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 usage context by mentioning 'supported currencies,' suggesting this tool is for discovering available currencies before using conversion tools. However, it lacks explicit guidance on when to use this versus alternatives like get_latest_exchange_rates or convert_currency_latest, leaving the agent to infer based on the tool name and description.

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