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

The description explicitly warns '取り消せません' (cannot be undone), reinforcing the destructiveHint annotation with a qualitative consequence. It also adds that the api_key must be issued from the admin console, which is useful auth context beyond the schema and annotations. No contradiction with the annotations was found.

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 front-load the action, immediately flag irreversibility, and state the auth requirement. There is no fluff or redundant restating of schema fields.

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 simple two-parameter destructive tool with 100% schema coverage and relevant annotations, the description captures the essential action, consequence, and auth need. It does not mention what happens to the associated user or how to locate the credential_id, but those gaps are minor at this complexity level.

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 description coverage is 100%, so the baseline applies: the schema already defines api_key and credential_id clearly. The description adds only minimal provenance for api_key ('管理画面で発行したキー') and does not meaningfully expand on credential_id beyond the schema.

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 verb and resource: 'パスキーを1本失効します' (revoke one passkey), and the singular '1本' makes the granularity clear. It does not explicitly contrast itself with sibling tools like revoke_user, but the resource type is specific enough to avoid obvious confusion.

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?

There is no guidance about when to use this tool versus revoke_user, issue_recovery_token, or list_credentials. The mention that an api_key is required is an authentication prerequisite, not a usage context or alternative-selection rule.

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