get_exchange_rate

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

With no annotations provided, the description carries full burden. It discloses key behavioral traits: returns a 'single rate number' (output format), 'No API key required' (authentication needs), and 'current mid-market' (rate type). It doesn't mention rate limits, error conditions, or data freshness, but provides useful operational 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?

Three concise sentences that each earn their place: states purpose, specifies return format, and discloses authentication requirement. No wasted words, front-loaded with core functionality.

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 2-parameter read operation with no output schema, the description provides good coverage: purpose, return format, and authentication context. It could mention data source or refresh frequency for completeness, but covers the essentials well given the tool's simplicity.

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 description coverage is 100%, so the schema already documents both parameters thoroughly. The description doesn't add any parameter-specific information beyond what's in the schema (both parameters are ISO 4217 codes). Baseline 3 is appropriate when schema does the heavy lifting.

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 verb ('Get'), resource ('current mid-market exchange rate'), and scope ('between two currencies'). It distinguishes from sibling tools by specifying it returns a 'single rate number' (vs. historical rates or authenticated rates) and 'No API key required' (vs. get_rates_authenticated).

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 provides clear context for when to use this tool ('Get the current mid-market exchange rate') and implicitly contrasts with siblings through 'No API key required' (vs. get_rates_authenticated) and 'single rate number' (vs. historical data). However, it doesn't explicitly state when NOT to use this tool or name alternatives directly.

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