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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is well covered. The description adds valuable behavioral context beyond annotations: the exact returned fields (facility name, address, coordinates, permit status, noncompliance quarters, inspection count, HPV flag), the public-domain source, and 'no auth required.' These details inform an agent's expectations without contradicting annotations.

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 structured and front-loaded, starting with the core action, then returns, use cases, parameter guidance, and source. Each sentence adds information (search behavior, fields, typical uses, parameter hints, provenance/auth). It is moderately sized but not bloated, with no repetition of schema details.

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?

For a search tool with a rich output schema, the description covers the key aspects: search modes, returned fields, use cases, and auth requirements. It does not discuss pagination or rate limits, and it does not explicitly route users to sibling tools like facility_detail for more granular data, but these are minor gaps given that the output schema and annotations carry significant information.

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%, with each of the four parameters documented in the schema (limit, state, zip_code, facility_name). The description adds almost nothing beyond the schema—it only reiterates the search modes ('zip_code' vs 'facility_name with state'), which the schema already states in the zip_code and state fields. This matches the baseline 3 for high schema coverage.

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 opens with a specific verb and resource: 'Search facilities regulated under the Clean Air Act (CAA) by ZIP code or facility name.' This clearly distinguishes it from sibling tools like echo.compliance.facility_search (general ECHO search), echo.compliance.facility_detail, and echo.compliance.violations by identifying the CAA air program scope.

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 clear context for when to use the tool, including search strategies ('Use zip_code for location search or facility_name with state for targeted search') and use cases ('air quality compliance monitoring, permit research, and environmental due diligence'). It does not explicitly state when-not to use it versus alternatives, but the context is otherwise clear.

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