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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered structurally. The description adds the verification use case and the 'registered agent' scope, but says nothing about failure behavior for an unknown ID, whether keys rotate, or freshness of the returned key. That is a modest addition beyond annotations, not a rich one.

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 no filler, and the return value is front-loaded ahead of the usage hint. The first sentence is a verbless fragment ('Public key and fingerprint of a registered agent ID'), which costs a little readability.

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 one-parameter, read-only lookup with full schema coverage, the description covers what is returned and why you'd call it. The only meaningful omission is what happens when the agent ID is not registered, which an agent would want to know before relying on the result.

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 coverage is 100% and the pattern plus example already fully document agent_id. The description restates the format ('br_ followed by 16 characters'), which reinforces the constraint but adds no meaning beyond the schema. 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 names the exact resource returned (public key and fingerprint) scoped to a registered agent ID, which is a specific enough statement of purpose. It is a noun phrase rather than a verb-led sentence, but an agent can still tell immediately what comes back. Sibling names (doorman, jobs, help_board, meta, quickstart) are distinct enough that lookup is unambiguous.

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?

It gives an explicit use case: check a key before sealing a message to that agent, which places the call in a concrete workflow. It does not name an alternative tool or state when not to call it, 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.