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

Annotations declare readOnly and openWorld, but the description adds material context beyond them: the $0.002 USDC cost per successful call via x402 (Base, Solana, Arc) and that failed calls are not charged. This payment/auth detail is genuinely useful for an agent deciding whether to invoke.

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, front-loaded with what the tool returns and followed by scope limits and pricing. Dense but every clause carries information; no filler.

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?

An output schema exists, and the description still summarizes the return shape (score 0-5, category label, country rank), plus covers source, scope, and pricing. An agent has enough to call it correctly; only an explicit alternative-tool pointer is missing.

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 the single 'country' parameter is documented as an ISO alpha-3 code in the schema. The description adds no format or syntax detail beyond what the schema already provides, so baseline 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?

Names a specific resource (WRI Aqueduct 4.0 country water-risk indicators) and enumerates the exact metrics returned (baseline water stress, depletion, variability, drought risk). It also scopes the tool explicitly by excluding sub-national/basin values, so an agent can distinguish it from any grid or drought sibling.

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?

Provides a clear usage boundary ('Sub-national (basin) values are not included') and specifies the default weighting, giving context for when the output applies. It does not name an alternative tool for basin-level needs, but no direct water-stress sibling exists in the list.

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