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

Annotations already declare readOnlyHint=true, and the description adds no contradictory behavior. It additionally explains the index composition, data sources (County Health Rankings + NCI), output fields, and county coverage, which are useful beyond the annotation.

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 sentences, front-loaded with purpose, then output, then input format and coverage. No redundant words.

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 single-parameter, read-only lookup, the description covers what the tool returns, how to specify the county, and data coverage. The lack of an output schema is mitigated by the explicit return description; 'band' is not defined but the description is otherwise self-sufficient.

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 schema fully documents the county parameter with both formats, and the description repeats these examples without adding new semantic details such as validation rules or edge cases. Thus the description provides no extra value beyond the schema.

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 opens with 'Composite county mortality risk index' and enumerates components (premature death, suicide, overdose, inverted life expectancy), clearly distinguishing this from sibling county_* risk tools. The return of 'national percentile rank and band' specifies the output.

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 input formats and coverage count, giving clear context for invocation. However, it does not explicitly mention when to prefer this tool over sibling risk indices such as county_cancer or county_sdoh, so alternatives are not excluded.

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