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

Annotations already declare readOnlyHint and idempotentHint, and the description does not contradict them. It adds useful behavioral context beyond annotations, such as the key history being append-only and the entry containing a current fingerprint and key version.

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 sentences with no filler. The read scope and content are front-loaded, and the actionable usage reminder follows naturally. 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?

For a simple read-only lookup with strong annotations, the description lists the key returned fields and a practical verification step. It does not explain output formatting or explicitly route to get_key_history for history-only needs, but that is a minor gap given the low complexity.

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%, with both parameters already described in the input schema. The description does not add parameter-specific syntax or formatting details beyond what the schema provides.

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 clearly states 'Read one participant's directory entry' and enumerates the contained data (public keys, fingerprint, key version, append-only key history), giving a specific verb and resource. It does not explicitly differentiate from the sibling get_key_history, which seems to overlap on key history.

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 final sentence gives a concrete use case: compare the returned fingerprint against the one pinned before encrypting. It does not name alternative siblings such as get_key_history or list_agents, nor does it state when not to use this tool.

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