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

Annotations only declare readOnlyHint=false and openWorldHint=true; the description adds the crucial behavioral fact that the old key is invalidated immediately, which the annotations do not convey. It stops short of saying whether rotation is reversible, whether old keys have a grace period, or that the caller must persist the returned key.

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?

One short sentence, front-loaded with the action and followed by the most important consequence. Nothing is wasted and nothing needs reordering.

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 single-optional-parameter tool with no output schema, the description covers what it does and the destructive side effect, which is the main risk an agent needs to know. A note confirming that the new key is returned in the response and whether the caller must have an existing valid key would make it fully self-sufficient.

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 sole parameter's description ('Only if your client cannot send the Authorization header') is already clear in the schema. The tool description adds no further meaning about the api_key parameter or its interaction with the rotation outcome, so 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 action and resource ('Get a new api_key') and immediately states the effect on the prior key, so the agent knows exactly what the call produces. No sibling tool in the list deals with credentials, so there is no ambiguity to resolve.

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?

Usage is only implied: an agent can infer it should call this when it needs fresh credentials, and there are no alternatives to route between. However, no explicit trigger ('call this when your key is compromised or expired') or precondition (which auth is required to rotate) is stated.

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