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

Adds substantial context beyond the readOnly/destructive annotations: result ordering (population served, largest first), the shape of each record (brief, includes current health-based violation count), and the absence of offset paging with a 500 cap. It does not discuss rate limits or what fields a 'brief record' contains beyond violations, which keeps it short of a 5.

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 dense sentences, front-loaded with the core action and narrowing options, then return behavior, then the routing instruction. No filler and nothing repeated from the schema for its own sake.

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 describing ordering, record brevity, and the violation count in results. With six optional params, the filtering model and the escape hatch to the detail tool, an agent has everything needed to call this correctly.

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%, so the baseline is 3, but the description adds operative meaning: county requires state, the type codes are the only valid values, and the limit interacts with the no-offset-paging design so the agent knows to filter rather than page. It largely restates the schema's own parameter docs, which caps it at 4.

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?

Specific verb+resource ('Search US public water systems') with the searchable facets and the scope ('US public') stated up front. It is clearly distinguished from the sibling get_water_system, which the description explicitly positions as the detail-retrieval counterpart.

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?

Explicitly states when this tool applies (name search with optional narrowing) and when to switch: 'Use get_water_system with a result's PWSID for that system's full profile, violations, lead/copper and PFAS detail.' It also prescribes the correct strategy when results are insufficient ('narrow the filters to dig deeper') rather than paging.

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