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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuinely useful behavioral context beyond that: the keys identify 'this issuer' and the operator must independently establish trust in that issuer, a security-relevant caveat not derivable from 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?

Two short sentences with zero waste; the purpose is front-loaded and the trust caveat follows immediately. Every sentence earns its place.

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?

An output schema exists, so return values need not be explained, and there are no parameters to document. The description is complete enough to call the tool correctly; it could go slightly further on key freshness/rotation or the expected trust-verification workflow, but nothing essential is missing.

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?

Zero parameters, so per the rubric the baseline is 4. There is nothing parameter-wise for the description to clarify, and it correctly adds no spurious parameter detail.

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?

States a specific verb ('Return') and resource ('public keys of this issuer'), so the agent can tell it apart from the receipt-issuing/verifying siblings, which operate on different artifacts. It does not explicitly name a sibling, but none is confusable with this one.

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 trust caveat implies the usage context (obtaining issuer keys to establish trust out-of-band), but there is no explicit when-to-use statement, no prerequisites, and no alternatives — there simply is no sibling alternative. Usage is implied rather than stated.

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