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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the safety profile is covered. The description adds a genuinely important security caveat not present in the structured data: the operator must establish trust in this issuer out-of-band, meaning the returned keys cannot be self-validating.

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, front-loading the action before the caveat, with no filler. Every sentence carries information the caller needs.

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 zero-parameter read tool with an output schema, the description need not explain return values, and the trust caveat covers the main non-obvious concern. The only gap is the absence of any hint about how the keys relate to the verify/prepare receipt workflow.

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 tool takes zero parameters, so the baseline is 4. The description adds nothing parameter-related, but nothing is required since there are no inputs to disambiguate.

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 states a specific verb ("Return") and resource ("public keys of this issuer"), which clearly separates it from the sibling tools that issue, prepare, and verify receipts. It is clear what the tool does, though it does not explicitly name or contrast itself with those siblings.

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?

There is no guidance on when to call this tool versus verify_agent_receipt or the other siblings, and no workflow context (e.g., fetch keys before verifying). The trust note hints at a precondition but is framed as a warning rather than usage direction.

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