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

Adds context annotations do not carry: the exact auth mechanism (bearer token in the HTTP Authorization header), the guarantee that credentials are never returned in the profile, and the side effect of refreshing last-seen time. That last point sits in mild tension with readOnlyHint=true (it mutates server state), though it is a well-known pattern rather than a genuine contradiction.

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?

Three sentences, each carrying distinct load: what it returns, the side effect, the credential-handling guarantee, and the auth requirement. No filler and the purpose is front-loaded.

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, return values need not be enumerated, and the description still covers auth, side effects, and sensitive-data handling. It omits error behavior for an invalid or expired token, which would round it out.

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 correctly spends its words on the implicit input instead: the bearer token in the Authorization header, which is the only thing the caller must supply.

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?

Specific verb and resource: 'retrieve your identity' plus the side effect 'refresh last-seen time.' The self-scoped framing ('your identity,' 'as the authenticated agent') implicitly separates it from the sibling get_agent, which presumably fetches an arbitrary agent, but that contrast is never stated outright.

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?

Usage is implied rather than stated: an agent infers it should call this to learn its own identity or bump its last-seen timestamp. No explicit when-not-to-use and no pointer to get_agent for other agents' profiles, leaving the agent to infer the boundary itself.

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