List Contact Segments

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

The readOnlyHint annotation already declares safe read behavior. The description adds value by instructing the agent not to surface IDs or creation dates unless specifically asked, which is a useful behavioral guideline beyond the annotation.

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 two sentences with no redundancy. The first states purpose, the second provides a concise behavioral instruction. Every word earns its place.

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 is a simple read-only list operation with full parameter documentation. The description supplements the missing output schema by telling the agent what not to return. It's sufficiently complete for the tool's low complexity.

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 schema has 100% parameter coverage, so baseline is 3. The description adds meaning by highlighting that contactId or email are the two ways to specify the contact, which clarifies parameter relationships not explicitly stated in the schema.

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 the verb 'List' and the resource 'all segments a contact belongs to in Resend', with the methods 'by contact ID or email'. This is specific and clearly distinguishes from sibling tools like list-segments, which lists all segments.

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 clearly implies the tool is for listing segments of a specific contact, which differentiates it from more general segment listers. It doesn't explicitly name alternatives or exclusions, but the context is unambiguous enough.

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