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

Annotations already cover read-only and open-world behavior, but the description adds genuinely non-obvious traits: the upstream source (ECHO REST service) and the billing model ($0.002 USDC per successful call via x402 on Base/Solana/Arc, failures not charged). That cost disclosure is material for an agent deciding whether to call. It does not cover rate limits or latency, which keeps it off 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 sentences, purpose and scope front-loaded, exclusion before the commercial note. The pricing sentence is long and slightly tacked on, but it carries useful decision information rather than 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?

With an output schema present, return-value detail is unnecessary, and the description supplies everything else an agent needs: data source, what granularity is and isn't available, single-state constraint, and full cost terms. Nothing essential to correct invocation 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 parameter is fully documented as a 2-letter US state code with an example. The description reinforces the single-state scope but adds no format or validation detail beyond the schema, so this is baseline territory.

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 the specific resource (EPA ECHO enforcement/compliance summary), the scope (one US state), and enumerates exactly what is returned: counts of active facilities, inspections, formal enforcement actions and total penalties. It also states the boundary — facility-level violation lists are not included — which separates it from a detail-level tool.

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 scope constraint ('for one US state') and the explicit exclusion ('Facility-level violation lists are not included') tell the agent when this tool is the wrong choice. It stops short of naming a sibling alternative for facility-level data, so routing for that case is left implicit.

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