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

Annotations already declare destructiveHint: true, so the bar is lower. The description adds the context of 'used to register new devices' but does not disclose that the key is secret and typically shown only once. No contradiction exists between description and annotations.

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?

The description is two concise sentences, front-loading the primary purpose and then providing the REST endpoint reference. No wasted words or repetition.

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?

The schema fully documents all 6 optional parameters, and the destructiveHint annotation covers safety. However, the description does not mention the response contents (e.g., that the auth key value is returned once), which is important for an agent to know. Overall adequate but with a notable 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?

Schema description coverage is 100%, so all parameters are described in the schema. The description itself does not add any parameter-specific meaning beyond what the schema already provides, 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?

The description clearly states a specific action ('Create a new auth key') and resource ('tailnet'), and includes the purpose ('used to register new devices'). It distinguishes from siblings like tailscale_delete_key and tailscale_list_keys by indicating creation.

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?

It gives clear usage context by stating the key is for registering new devices, implying when to use this tool. It does not explicitly name alternatives or exclusions, but the purpose is unambiguous enough that usage is clear.

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