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

Annotations already indicate a read-only, idempotent, non-destructive operation. The description adds meaningful behavior beyond that: the result includes revoked passkeys and distinguishes them by revoked_at, and it discloses an authentication requirement for api_key. No contradiction with annotations.

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 one compact, front-loaded sentence with a short parenthetical auth note. Every phrase contributes information: operation, resource, inclusion of revoked items, distinguishing field, and required key.

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 read-only list tool with two documented parameters, the description covers purpose, the revoked-inclusion caveat, the distinguishing field, and the auth requirement. There is no output schema, but the description gives enough expectation of the return shape without needing exhaustive detail.

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%, so both parameters are already fully documented. The description adds minimal extra context by tying external_id to '利用者' and clarifying that api_key is issued from the admin console, but it does not add significant meaning 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 specific verb and resource: returns a list of a user's passkeys (by external_id). It also distinguishes itself from siblings like list_users and revoke_credential by clearly scoping to passkeys and mentioning revoked_at.

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?

It gives clear context: use this to retrieve passkeys for a given external_id, noting that revoked passkeys are included and that an api_key from the admin console is required. It does not explicitly name alternatives or when-not-to-use cases, but the resource scope makes the intended use unambiguous.

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