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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds genuinely new context the annotations lack: it is available on the Free plan and functions as an API-key sanity check. It does not describe return ordering or format, but for a trivial list tool this is adequate.

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 compact sentences with no waste; the core purpose (all supported carrier keys) is front-loaded, followed by the operational caveat about the Free plan.

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?

No output schema exists, but the description conveys what is returned (carrier keys with examples) and when the call is useful. For a no-parameter enumeration tool this is nearly complete, missing only trivial detail like ordering or count.

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 takes zero parameters, so the schema requires no documentation and the baseline is 4. The description's parenthetical example keys add meaningful value by showing the shape of the returned values.

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?

States a specific verb (list) and resource (insurance carrier keys) and even enumerates example values (aetna, cigna, bcbs, medicare). It is clearly distinguishable from siblings like get_coverage or find_providers, though it never explicitly contrasts itself with them.

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?

Provides concrete usage context: it works on the Free plan and serves as an API-key sanity check, implying it should be called to validate credentials or discover valid carrier keys before using coverage tools. No explicit when-not or named alternative, so short of a 5.

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