Update device key

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true, so the mutation and safety profile are covered. The description adds the practical effect (disabling key expiry for servers) but does not disclose potential side effects, permission requirements, or impact on existing connections. With annotations providing the core safety traits, this is adequate but not rich.

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 efficient sentences with zero redundancy. The primary action and use case are front-loaded, and the description avoids unnecessary detail. It earns its place without wasting tokens.

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 2-parameter mutation tool with no output schema and moderate annotations, the description covers the essential purpose and a canonical use case. It does not explain return values or error conditions, but those are less critical for a straightforward update operation. The tool's scope is clear and sufficient for correct invocation.

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 description coverage is 100%, with both parameters well-documented (deviceId explains the format and clarifies it's not the nodeKey; keyExpiryDisabled is self-explanatory). The description adds no additional parameter detail beyond the schema, so the baseline of 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 clear verb (update) and resource (device's key settings), provides a concrete example (disabling key expiry), and identifies a specific use case (servers that should never re-authenticate). This distinguishes it from siblings like tailscale_expire_device (which expires keys) and tailscale_update_key (which manages API keys).

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?

Gives a clear usage scenario ('Useful for servers that should never need to re-authenticate') that helps an agent decide when to apply this tool. It doesn't explicitly name alternatives or when NOT to use it, but the context is strong enough for typical selection. Sibling differentiation is implicit through the specific focus on key expiry settings.

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