Get Exchange Rate

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

Annotations provide readOnlyHint=true, but the description adds valuable behavioral context beyond that: the session is auto-acquired and auto-releases after idle. This informs the agent that no explicit session setup is needed and that the tool is a safe read operation. It does not describe the return format, but for a simple getter with read-only annotation, this is acceptable.

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 remarkably concise: two sentences that front-load the primary purpose and then add a useful session note. There is no filler or redundancy, and every word contributes to understanding the tool's behavior.

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 simplicity (two string parameters, read-only, no output schema), the description is nearly complete. It covers the function and session lifecycle. The only slight gap is that it does not specify the return format, but unlike complex tools, the return is likely self-explanatory (a numeric exchange rate). Thus, it is almost fully 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 input schema already contains full descriptions for both parameters (source and target) with examples, achieving 100% schema coverage. The description does not add any new semantic information about the parameters beyond what the schema provides, so the baseline score of 3 applies.

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 function: 'Get the current exchange rate between two currencies.' It uses a specific verb and resource, and it is distinct from all sibling tools, which focus on accounts, positions, market data, and other resources. This makes the purpose unambiguous and differentiates it from 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 implicitly conveys when to use the tool (whenever an exchange rate is needed between two currencies), and the niche is unique among siblings, so no explicit alternatives are necessary. It also adds a practical constraint: 'Requires brokerage session (auto-acquired, auto-releases after idle),' which sets expectations for use. However, it does not elaborate on when not to use it or mention exclusions, which would push it to a 5.

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