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

Beyond the destructiveHint annotation, the description adds rich detail: it explicitly warns that the current key is 'IRREVERSIBLY deactivated' the moment of success, that other callers using the key stop working, that the new key is returned 'exactly once' and cannot be retrieved again, and that child keys cannot rotate themselves. These are critical behavioral traits that an agent must know before invoking the tool.

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 front-loaded with the action, immediately followed by the most critical warning. Each sentence serves a distinct purpose (action, warning, return behavior, constraint, auth). It is slightly long but all content is relevant and non-redundant. A 4 reflects good structure with minimal fluff.

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-parameter optional tool with no output schema, the description covers the essential operational context: the irreversibility, the uniqueness of response, the child-key limitation, and the auth requirement. It doesn't describe failure modes or the exact response format, but these are minor given the explicit warning and the schema's parameter documentation. The description is effectively complete for safe invocation.

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 input schema has 100% coverage for the single parameter (expires_in_days) with a clear description of its meaning and default. The tool description does not add any parameter-specific detail, but since the schema fully documents it, the baseline of 3 is appropriate. No extra value is added, but none is needed.

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 states a clear action: 'Replace the API key making this call with a fresh one carrying the same scopes.' The verb 'replace' and the resource (API key) are specific, and it distinguishes itself from related tools like mint_child_api_key by noting that child keys cannot rotate themselves. This leaves no ambiguity about what the tool does.

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 provides strong when-not guidance with the WARNING about not using on shared credentials and the note that child keys cannot rotate themselves. It also states the auth requirement. However, it does not name alternative tools (e.g., 'use mint_child_api_key for creating a new child key'), so the context is clear but lacks explicit cross-referencing.

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