passkey_save_registration

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

No annotations are provided, so the description must fully disclose behavioral traits. It does state the main side effect (saving to macOS Keychain), but it does not mention whether the captured credential is consumed/cleared from the virtual authenticator, whether repeated calls overwrite data, or whether any prior setup is required. This is a meaningful gap for a state-changing 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 a single sentence with no filler. It front-loads the action and destination, and every part contributes to understanding what the tool does.

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 tool with no output schema and no annotations, the description lacks important context: it does not explain the required ordering relative to passkey_enable_virtual_authenticator, what happens to captured credentials, or how it differs from keychain_store_credential. An agent would struggle to know when exactly to invoke this tool in a multi-step browser/passkey flow.

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%, and the description adds no parameter-specific meaning beyond what the schema already provides. The rpId and account descriptions are sufficient for understanding their values, so a baseline score of 3 is appropriate.

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 clearly states a specific verb ('Captures... and saves') and a specific resource ('newly registered Passkey credentials from the virtual authenticator', 'macOS Keychain'). It is easy to understand what the tool does, though it does not explicitly contrast itself with sibling tools like keychain_store_credential.

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 phrase 'newly registered Passkey credentials' implies this tool is used after a passkey registration flow, but there is no explicit guidance about when to choose it over alternatives like keychain_store_credential or how it fits with passkey_enable_virtual_authenticator. Usage context is only implied, not stated.

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