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

With no annotations, the description carries the full behavioral burden and does so well. It reveals that values are never exposed, that delivered_at may be null for vaulted secrets, that the field list itself is sensitive and requires proof of ownership, and that the operation is free. This gives the agent a strong model of access, privacy, and response behavior.

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 and front-loaded, leading with the core action and then adding return semantics, privacy guarantees, cost, and auth in a logical order. Every sentence earns its place with no redundant filler.

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 is complete for a read-only list tool: it explains what is returned, when fields are null, that values are never exposed, the sensitivity and auth requirement, and the cost model. An output schema exists so return-structure details are covered elsewhere.

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 schema already documents both npub and dpop_token thoroughly, including the exact framing requirements for dpop_token. The tool description adds the contextual point that proof of npub ownership is required, but it does not need to repeat parameter syntax. Baseline 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 opens with a specific verb and object: 'List stored patron credential field names (not values).' It immediately distinguishes this from value-returning or mutating credential tools by stating values are never exposed and framing the purpose as verification of configured fields and their ages.

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 gives a clear use case: 'use this to verify which fields are configured and how old each one is.' It also notes the prerequisite of npub ownership proof. However, it does not explicitly mention sibling tools as alternatives or state when not to use this tool, so it stops short of full usage guidance.

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