Identity of this host

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description's 'Read-only' adds no new safety information. The only extra context is the underlying CLI invocation (`tailscale whoami --json`), which is minor and does not describe output behavior or auth needs beyond what annotations already cover.

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 very short sentences with zero waste; the purpose is front-loaded and the parenthetical CLI hint is appropriately compact.

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, zero-parameter, read-only tool with no output schema, the description gives enough to know what it returns at a high level. It could be slightly richer about what identity fields are included, but nothing essential to calling it correctly is missing.

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?

There are zero parameters, so the schema carries no burden and the baseline is 4. The description adds no parameter information, but none is needed for a parameterless tool.

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 ('Show') and resource ('machine + user identity of this node'), making clear it returns the local node's identity rather than another node's. It does not explicitly name a sibling like tailscale_whois or tailscale_status to sharpen the boundary, but 'of this node' is enough to distinguish it from remote-identity tools.

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?

No when-to-use or when-not-to-use guidance is given, and no alternatives are mentioned. The agent can infer the purpose from the title, but the description provides no routing information against siblings such as tailscale_status or tailscale_whois.

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