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

With no annotations provided, the description carries the full burden of behavioral disclosure. However, it only states the data domain ('Eligible asset rates and yields') and does not disclose whether this is a read-only lookup, how data is returned, update frequency, or any access constraints. This is insufficient for a tool with no structured annotation safety info.

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 exceptionally concise with two short sentences. The first sentence states the regulatory context, and the second clarifies the data content. Every word earns its place, and the structure is front-loaded with the most distinctive 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?

Given the tool's low complexity (no parameters, no output schema), the description provides enough to know what domain it covers, but 'Eligible asset rates and yields' is somewhat vague. It does not specify whether these are current values, historical series, or specific rate types (e.g., €STR, EONIA), which would be helpful for an agent to fully understand the return value. It is adequate but not thorough.

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 zero parameters, so the baseline is 4. The description adds meaningful domain context beyond the empty schema by specifying that this tool provides eligible asset rates and yields for MiCA compliance, which helps the agent understand what the tool conceptually represents even without parameters.

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 identifies the tool as ECB data for MiCA stablecoin reserve compliance, specifying the relevant articles (24/25/53). It distinguishes from sibling tools like ecb_yields and ecb_fx by focusing on the MiCA regulatory context, though it lacks an explicit verb like 'retrieve' or 'list'.

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 phrase 'relevant for MiCA stablecoin reserve compliance' implies the intended use case, but there is no explicit when-to-use guidance, nor any mention of alternative tools or when not to use this tool. It leaves the agent to infer when this should be selected over the many sibling ECB tools.

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