tailnet_join

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

With no annotations, the description carries the full burden and does so unusually well: it discloses the auth path (fresh one-time key from TAILSCALE_API_KEY, generated only on apply, passed via environment and never persisted to plan/journal, with TAILSCALE_AUTH_KEY fallback), the exact effect (`tailscale up --reset --ssh --hostname node-<name>` plus exit node), and a post-run verification step. Secret handling, side effects, and confirmation behavior are all surfaced.

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?

Four dense sentences, front-loaded with the action and scope, then the auth mechanism and the executed command. Information-dense with little waste, though it is longer than strictly necessary for the front-loaded portion to land.

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?

No output schema or annotations, so the description must stand alone — and for a 7-parameter mutation tool it covers credentials, mechanism, and verification well. Remaining gaps (error modes, permissions required, consequences of --reset on existing state) are minor but real.

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 86%, so the parameters are already largely documented. The description reinforces the apply/host semantics ('key made only on apply', bootstrap.address) but adds no syntax or format beyond what the schema states, so this is baseline-level.

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 (Join) and resource (a server to the tailnet) plus the connection path (hosts.<name>.bootstrap in fleet.yaml). It also pins the eligibility window — 'already set up but logged out of Tailscale or never joined' — which implicitly separates it from node_bootstrap (fresh servers) so an agent can route correctly.

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 when-to-use condition (machine already set up but logged out, or never joined), which is the key routing signal. It never names the alternative (node_bootstrap) explicitly nor states when NOT to use this tool, so it stops short of full alternative routing.

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