passkey_fields

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly states that it does not reveal secret values (a safety-related behavior), describes the return format, and documents exception conditions (entry not found, keychain access failure). This is comprehensive for a read-only 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 well-organized into Args, Returns, and Raises sections, making it easy to scan. Every sentence provides useful information, with no filler or redundancy. It is appropriately sized for the tool's complexity.

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?

The description fully covers the tool's purpose, usage context, parameter meaning, return value behavior, and error conditions. With a single required parameter and an output schema, this description leaves no critical gaps for an agent to misuse the tool.

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 schema has 0% description coverage, so the description must compensate. It does so by providing a clear, contextual definition for entry_name, including an example ('slack') and a realistic return example. This adds meaningful semantic information beyond the bare 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 clearly states 'List field names in a passkey entry' with a specific verb and resource, and also emphasizes the key behavior of not revealing values. This distinguishes it from sibling tools like passkey_list (which likely lists entries) and passkey_status (which likely checks status).

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 explains that this tool is useful for 'discovering what secrets are available without exposing the actual secret values,' which implies when to use it. However, it does not explicitly state when not to use it or name alternative tools, so it lacks explicit exclusions.

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