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

No annotations are provided, so the description must stand alone. It adds the fact that there are exactly 39 counties and that the purpose is to find names for filtering, but it does not disclose return format, ordering, or any edge cases. Given the simplicity, the information is adequate but not extensive.

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 exactly two sentences, front-loads the core capability ('List all 39 Washington State counties'), and the second sentence adds useful context. There is no wasted verbiage.

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 trivial parameterless list tool, the description covers the core purpose and the primary use case. It doesn't specify the exact response format, but given the simplicity and the sibling search_resources tool, the intent is clear. A score of 4 reflects it's complete for its complexity.

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, and the input schema is an empty object. The description does not need to explain any parameters, and the baseline for zero-parameter tools is 4. No irrelevant parameter information is included.

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 explicitly states 'List all 39 Washington State counties' with a specific verb and resource, and the count adds specificity. It clearly distinguishes itself from sibling tools by focusing on enumeration of counties rather than getting or searching resources.

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 second sentence 'Use this to find the correct county name for filtering search results' provides a clear use case and implies when to choose this tool over alternatives. It does not explicitly mention when not to use it or name alternative tools, so it falls just short of the highest standard.

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