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

With no annotations provided, the description carries full responsibility for behavioral disclosure. It reveals that the tool is free, requires proof of npub ownership, never exposes values, and returns null delivered_at timestamps for vaulted secrets before timestamp recording—details beyond the schema and 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 compact and front-loaded with the main purpose. Each sentence earns its place: clarifying 'not values,' describing output timestamps, noting the free tier, and explaining the auth requirement and sensitivity. No redundancy or fluff.

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?

Given the tool's low parameter count and the presence of an output schema, the description is remarkably complete. It covers purpose, output semantics, cost, authentication prerequisites, and the sensitivity rationale. There is no missing critical context typically needed for safe invocation.

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 a baseline of 3 is appropriate. The description adds a brief note that npub ownership proof is required, which relates to dpop_token, but this is more behavioral context than parameter semantics. The schema's own dpop_token description is already highly detailed.

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 precise verb and resource: 'List stored patron credential field names (not values).' It clearly distinguishes this read-only listing tool from sibling mutation tools like excalibur_delete_patron_credential and excalibur_update_patron_credential, and specifies the output scope (field names plus delivered_at timestamps).

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 states an explicit use case: 'use this to verify which fields are configured and how old each one is.' It also implies a when-not by noting 'Values are never exposed,' but it does not explicitly name alternative tools for retrieving values, so it falls short of full when/when-not coverage.

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