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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description's added value is the BYOK cost model (inference billed to the user, routing handled by the platform) rather than behavioral detail such as what the listed entries contain or whether the set is static.

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 short sentences with the core purpose front-loaded. The second sentence is partly promotional but does convey the cost/billing model, which is decision-relevant for a BYOK tool.

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?

With zero parameters, rich annotations and an output schema, the description needs only to establish scope, which it does. It could be slightly stronger by stating that the results are the provider identifiers expected by set_llm_key, but nothing essential is missing.

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 no parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The mention of "keys" correctly signals this is the provider catalog rather than a keyed operation.

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?

Clear verb+resource ("List LLM providers") with the added qualifier that these are BYOK-eligible providers. It implicitly separates itself from list_llm_keys (configured keys) and set_llm_key (writing a key), but never names those siblings, so differentiation requires inference.

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 phrase "providers you can bring keys for" implies the use case (discover options before calling set_llm_key), but there is no explicit when-to-use statement, no exclusion, and no named alternative for the adjacent case of inspecting already-stored keys.

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