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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and closed-world scope, so the safety profile is covered. The description adds a meaningful trust-model caveat (verify issuer trust independently rather than blindly trusting these keys), but says nothing about rotation, caching, or key format.

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 the action front-loaded and the trust guidance second; every word earns its place and there is no 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?

With an output schema present and no inputs, the description does not need to explain return values or arguments. It is nearly complete for a simple key-fetch endpoint, though it omits any note on key rotation or freshness an agent might care about.

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 there is no argument semantics to explain and the baseline is 4. The description correctly adds no redundant parameter talk.

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 and resource ('Return issuer public keys'), which is unambiguous and clearly distinct in function from the sibling verbs issue/prepare/verify. It does not, however, explicitly reference any sibling or scope boundary, so it stops short of full differentiation.

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?

'Establish issuer trust independently before offline verification' positions the call in the workflow, implying it precedes verify_api_receipt and supports offline verification. It gives clear context for when the tool is needed but names no explicit alternative or exclusion.

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