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

Annotations already establish this as a safe read-only, non-destructive, non-open-world operation. The description adds useful behavioral context about what the tool returns: exact field names, types, accepted operators, and picklist options. It stops short of describing result shape or pagination, but that is a minor gap given the annotations and simple discovery scope.

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 a single front-loaded sentence with no filler. Its colon-delimited list efficiently communicates the returned field metadata.

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 simple, read-only discovery tool with one fully described optional parameter and no output schema, the description is largely complete because it explains the returned metadata. It could be stronger if it clarified the result shape or the effect of omitting search_keywords, though the schema covers the latter.

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%, so the single optional search_keywords parameter is fully documented in the schema. The description does not mention search_keywords or explain how keyword matching affects the catalog, so it adds no parameter semantics beyond the schema baseline.

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 (Discover) and resource (fields an Insights/Spotlight account-journey segment can filter on), and enumerates the returned metadata: field names, types, operators, and picklist options. It is clear, but it does not explicitly distinguish this from nearby criteria-search or segment-criteria siblings.

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?

Usage is strongly implied: call this to discover filterable Insights segment fields before constructing criteria. However, the description gives no explicit when-to-use/when-not-to-use guidance and names no alternative tools such as search_target_group_criteria or get_segment_criteria.

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