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

Annotations already indicate this is a mutation (readOnlyHint false), and the description adds the static/dynamic distinction. It doesn't disclose downstream requirements like populating static segment members via set_segment_members, but the description adds moderate value beyond 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?

Two concise sentences. The first states the action, the second explains the key type decision. No wasted words or filler content.

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 output schema exists and annotations clarify it's a write operation. The description is minimal but the schema covers the complex criteria structure. It could mention that STATIC segments require later member assignment via set_segment_members, but this is not a critical omission for basic usage.

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%, so parameters are well-documented. The description adds meaning to segmentType by explaining that STATIC is for manual member lists and DYNAMIC is for criteria-based auto-filtering, which goes beyond the schema's simple enum label.

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 clearly states 'Create a new customer segment' with a specific verb and resource. It also distinguishes the two segment types (STATIC vs DYNAMIC), which helps differentiate it from sibling segment-related tools like set_segment_members or preview_segment_count.

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?

It provides clear context on when to use STATIC vs DYNAMIC segment types, which is useful for parameter selection. However, it does not explicitly contrast with alternatives like update_segment or set_segment_members, though the tool name and siblings make this somewhat implicit.

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