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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is well covered. The description adds the scope 'every searchable carrier' and mentions returned data (plan counts, networks), which gives some behavioral context. However, it does not disclose potential performance implications (e.g., large result set) or any other behavioral traits beyond what annotations state. This is sufficient but minimal.

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, information-dense sentence. It front-loads the main action and includes the key output details without any fluff. Every word contributes value, and it is appropriately concise for a tool with no parameters.

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 simplicity (no parameters), the presence of an output schema, and rich annotations covering safety and idempotency, the description is complete. It states exactly what is returned (carriers, plan counts, networks) and the scope (all searchable carriers). An agent has all necessary information to decide whether to call this tool and what to expect.

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 tool has zero parameters, so the description naturally adds no parameter-specific meaning. The baseline for zero-parameter tools is 4, and the description adequately covers the tool's purpose without needing parameter details. There is no gap here.

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 verb 'List' and the resource 'carriers', and specifies that it includes plan counts and networks. It is unambiguous about what the tool does, though it does not explicitly differentiate from sibling tools like search_plans or get_plan_details. Since the purpose is specific to carriers, it is clear enough to be distinguished by an agent.

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 implies usage when one needs a catalog of carriers, but provides no explicit guidance on when to choose this over sibling tools such as search_plans or compare_plan_costs. There are no exclusions or alternative references, leaving the selection to inference. This is adequate but not thorough.

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