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

With no annotations at all, the description carries the full disclosure burden. It hints at a pricing/access trait ('free sample') but never says which carrier is returned, whether the sample data is fixed or genuinely real, whether the call is read-only, or whether there are call limits.

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 short sentence with no filler and the key differentiator front-loaded. It is efficient, though the extreme brevity leaves important context unstated.

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 zero-parameter tool with no annotations and no output schema, the description covers the essential shape relationship to the sibling. It still leaves open which carrier is sampled and whether the returned answer is real, which matters for an agent deciding whether to trust the output.

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 takes zero parameters, so the baseline is 4 and there is nothing for the description to clarify. No parameter-related misinformation is present.

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 says it returns a real answer for one carrier with the same shape as mcs150_lookup, which does distinguish it from its sibling as a sample/trial variant. However, there is no verb describing retrieval and no explanation of what an 'mcs150' answer actually contains, so the purpose is only loosely conveyed.

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?

'Free sample' plus 'same shape as mcs150_lookup' implies usage as a preview or test call before the real lookup, which is a usable hint. There is no explicit when-to-use/when-not statement, no mention of cost limits, and no guidance on when to graduate to mcs150_lookup.

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