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

Annotations already declare readOnlyHint and openWorldHint, so the bar for additional disclosure is lower. The description adds the 'current' aspect, implying live data, and documents the base_currency parameter, but does not cover error handling, rate limits, or return structure, leaving some behavioral aspects unspecified.

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 extremely concise, consisting of a single sentence for the purpose and a short args list. It is front-loaded and contains no extraneous text, making it highly efficient.

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 tool with one optional parameter and no output schema, the description covers the core purpose and parameter semantics. However, it does not describe the return format or the set of supported currency codes, which could leave the agent uncertain about how to interpret the response.

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 0% description coverage, but the description compensates by defining 'base_currency: Base currency code (default 'USD')'. This clarifies the parameter's meaning and default value, though it does not specify the exact format (e.g., ISO 4217), leaving some ambiguity.

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 'Get current currency exchange rates' clearly states the action (get) and resource (currency exchange rates), distinguishing it from the sibling 'crypto_prices' by focusing on fiat exchange rates. It does not explicitly name the sibling alternative but the purpose is 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?

Usage is implied by the purpose: the agent should use this tool when it needs current exchange rates. However, the description provides no explicit guidance on when to use it versus crypto_prices, and no exclusions or alternative scenarios are mentioned.

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