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

Beyond the readOnlyHint annotation, the description discloses substantive behavioral details: the scoring methodology (z-scored against trailing 90-day baseline windows), the 14-day entry-lag guard, the specific return fields, and the daily update cadence. This gives the agent a strong expectation of what the tool computes and how.

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 concise and well-structured: it opens with the primary output, explains the methodology, lists return components, gives usage scenarios, and ends with update frequency. Every sentence contributes new information without redundant padding.

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?

Although there is no output schema, the description enumerates all returned fields and the score calculation logic. The optional history parameter is fully documented in the input schema, and the tool's purpose and safety profile are clear. The description is complete for a read-only risk-scoring tool.

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?

Schema description coverage is 100% for the only parameter 'days', including its purpose, minimum/maximum, and tier requirement. The tool description itself adds no parameter-level detail, so the baseline of 3 applies.

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 immediately states the tool 'Returns a 0-100 water compliance risk score' and specifies the underlying data (EPA ICIS, 90-day windows, lag guard) and output components (CWA, SDWA, federal-penalty counts, baseline stats). This clearly defines the tool's distinct role among siblings like adw.county_water or adw.air_quality_risk.

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 explicit usage triggers: 'Call when the user asks about EPA water enforcement intensity, Clean Water Act or Safe Drinking Water Act risk, or when timing environmental audits, discharge-permit reviews, or water-utility exposure decisions.' However, it does not name alternative tools or state when not to use this tool, so it lacks the exclusions needed for a 5.

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