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

Beyond the annotations (readOnly=false, idempotent=false), the description discloses the crucial side effect that the old key stops working immediately and that the caller must persist the new key. This is exactly the kind of irreversible consequence an agent needs before calling. It stops short of saying whether existing sessions or other agents are affected, but the core behavior is well covered.

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?

Three short sentences, front-loaded with the decision trigger, then the effect, then the follow-up action. No redundant wording and nothing repeated from the schema or title.

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?

For a one-parameter tool with annotations but no output schema, the definition covers the return value, the irreversible effect on the old key, and the required follow-up of saving the new key. Only minor gaps remain, such as propagation timing across sessions.

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?

Schema coverage is 100% and the single api_key parameter is fully documented in the schema, including the Bearer-header alternative. The description adds no extra meaning about the parameter (e.g., it doesn't say the input key is the one being rotated), so the baseline 3 applies.

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 names a specific verb and resource ('rotate'/'api_key' via title) and states the concrete outcome: a new api_key is returned and the old one stops working. It does not explicitly differentiate itself from any sibling, but no sibling in the list is a competing key-management tool, so ambiguity is low.

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?

'Use this if your key may have leaked' gives a clear triggering condition for invocation. There are no exclusions or named alternatives, but the trigger is explicit enough that an agent knows when this tool applies rather than check_in or register_agent.

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