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

Annotations already declare destructiveHint=true, so the safety profile is covered. The description usefully adds what the destruction actually means — the node key is invalidated and the device must re-authenticate — which is behavioral detail beyond the annotation, though it omits whether the device entry/data survives.

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 tight clauses with the core action and the motivating scenario front-loaded, followed by the endpoint reference. 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?

For a single-parameter mutation with no output schema and destructiveHint already set, the description supplies the action, the rationale, and the endpoint. It leaves the device-id format and post-expiry state unstated, a minor gap.

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?

Only one parameter (deviceId) with 100% schema description coverage, so the schema already carries the semantics. The description references deviceId only implicitly via the REST path and adds no format or sourcing detail, so baseline 3 applies.

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 (expire) and resource (device's node key), plus the concrete consequence (forces re-authentication). This clearly separates it from siblings like tailscale_delete_device or tailscale_delete_key, which have different destructive semantics.

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?

Explicitly frames the use case: 'a security response to a compromised or lost device.' That is clear context for when to reach for this tool, but it does not name the alternative actions (delete device vs. delete key) or state when not to use it.

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