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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds useful behavioral context by stating 'no auth required' and 'US Gov public domain,' which are not in the annotations. It does not contradict annotations and provides additional information beyond the structured data, though it omits rate limits or response size, which are less critical for a single-record lookup.

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 three sentences with no redundancy: the first states purpose and return fields, the second explains the workflow, and the third gives use cases and source/auth. It is front-loaded with the core action and keeps every sentence valuable.

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?

The tool has an output schema, so explaining return values is not required, but the description lists them anyway. It also covers the source of the Registry ID, the workflow, use cases, and authentication requirements. For a single-parameter lookup tool, nothing an agent needs to call it correctly 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?

The input schema already documents the registry_id parameter thoroughly, including an example and source. The description reinforces this by adding 'Registry IDs are obtained from echo.compliance.facility_search results,' which is extra workflow context beyond the schema. With 100% schema coverage, the baseline is 3, and this addition justifies a 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?

The description states a specific verb ('Retrieve') and resource ('detailed compliance profile for a specific EPA-regulated facility by Registry ID'). It distinguishes from sibling tools like echo.compliance.facility_search by specifying that this is a detail lookup and that Registry IDs come from search results. It also lists the specific return fields, making the purpose unambiguous.

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 description explicitly states that Registry IDs are obtained from echo.compliance.facility_search, implying a clear workflow: search first, then retrieve detail. It also notes the tool is 'essential for due diligence, ESG screening, and permit verification,' providing context for when to use it. However, it does not explicitly contrast with other siblings like violations or air_facilities, so it falls short of a 5.

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