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

With no annotations, the description carries the full behavioral burden, and it does disclose two real traits: the data is 'real-time' and no API key/auth is required. It omits rate limits, behavior on invalid or unknown currency codes, and whether the result is a rate or a converted amount, so the disclosure is partial.

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?

A single front-loaded sentence with zero padding; the key capability and the auth-free trait both land immediately. Nothing could be trimmed without losing information.

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 is simple (3 required, fully documented params), but with no output schema the description should state what comes back — a rate, a converted amount, or both — and it does not. Error handling for bad currency codes is also unaddressed, leaving a real gap for a network-backed lookup.

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 amount, baseCurrency and targetCurrency are already fully documented with examples. The description adds no parameter-level meaning beyond the schema, which is the expected baseline of 3.

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?

States a specific verb-and-resource: 'foreign exchange rate conversion' on currency, plus the distinguishing trait 'real-time'. It cannot be confused with its siblings, all of which are media/file converters. It stops just short of 5 because it doesn't say whether the tool returns a converted amount or only the rate.

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?

There is no when-to-use or when-not-to-use guidance, and no alternatives are named. The sibling list is all media tools, so routing risk is low, but the description offers no context for selecting this tool over anything else.

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