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

The description discloses important behavioral traits beyond the annotations: 'criteria replaces the existing rules' indicates a full replacement rather than merge. It aligns with the idempotentHint annotation ('Pass only the fields to change'). No contradictions with 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 highly concise with two well-structured sentences. The first sentence states the core purpose, and the second adds critical usage context. No extraneous text.

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?

Given the tool's moderate complexity and that an output schema exists, the description covers essential behavioral aspects (partial update, criteria replacement). It does not mention required permissions or prerequisites, but for a standard update tool, this is acceptable.

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?

With 100% schema description coverage, the schema fully documents each parameter. The tool description adds semantic value by explaining the partial update pattern and the replacement behavior for criteria, which goes beyond what the schema provides.

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 the action ('update'), the resource ('existing customer segment'), and the method ('by id. Pass only the fields to change'). It effectively distinguishes from sibling tools like create_segment or delete_segment.

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 provides clear guidance on partial updates ('Pass only the fields to change') and specifies that 'criteria replaces the existing rules'. It does not explicitly state when to use this tool versus alternatives, but the sibling context offers some implicit differentiation.

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