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

Annotations already cover the read-only, idempotent, non-destructive profile, so the bar is lower, and the description still adds real behavioral context: matching is approximate because service boundaries are not public, and the authoritative source is the user's water bill. It does not cover pagination or result-size behavior, but the key caveat is disclosed.

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?

Two sentences with zero padding. The scope statement comes first and the accuracy caveat second, which is the right front-loading for a lookup tool.

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?

No output schema exists, and the description compensates by naming what comes back (SDWA violation summaries) plus the approximation caveat. Safety semantics are covered by annotations, so little is missing; only result shape/pagination detail is absent.

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 coverage is 100% and all three parameters carry their own descriptions, so the schema does the heavy lifting. The description adds the combination semantics ('state + county and/or city'), which slightly clarifies that city and county can be used independently or together, but no format or edge-case detail beyond that.

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 states a specific verb+resource (look up public water systems), the scope (a US state plus county and/or city), and the payload (health-based SDWA violation summaries). It is clearly distinct from the sibling tools due_diligence and environment_near, though it never explicitly names them.

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?

Usage is implied by the resource description, but there is no explicit when-to-use vs. when-not or any reference to the alternatives (due_diligence, environment_near). The note about the water bill points at a fallback when matching fails, which is a useful hint but not a full use-condition.

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