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

Even though readOnlyHint=true already signals a safe read, the description adds substantial behavioral context: the trailing 5-year range, 70/30 weighting with YoY direction, higher=worsening, the ~4-6 month lag, monthly updates, and the meaning of reported fields. This goes well beyond the annotation's minimal safety signal.

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 dense but well-structured, front-loading the core value proposition, then listing returned fields, then the use cases, and finally the update frequency. Every sentence adds meaningful information; no filler or redundancy.

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?

Despite no output schema, the description lists the specific returned fields (index, prior-year counts, yoy_change, predicted_count, recent_months, reporting_period), explains the index scoring, and notes the data lag. This is complete for an agent to understand what the tool does and what data it returns.

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 input schema has 100% description coverage for the single optional 'days' parameter, including its purpose, range, and Gold-tier requirement. The description does not add extra parameter semantics, which is fine since the schema already does the heavy lifting. Baseline 3 is appropriate.

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 returning a 0-100 US drug-overdose mortality index and enumerates the exact output fields. The verb 'Returns' with a specific resource and data source (CDC NCHS VSRR) distinguishes it from generic or sibling tools.

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?

Explicit when-to-use guidance is provided: 'Call when the user asks about overdose deaths, the opioid crisis, or drug-mortality trends, or when timing behavioral-health capacity, naloxone supply, or settlement-fund decisions.' However, it does not mention when not to use it or name alternative sibling tools.

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