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

Annotations declare readOnlyHint=false with idempotentHint=true, which is a slightly unusual pairing for a tool described as a 'check'; the description resolves this by explaining that the call yields the download link, QR code image link, pairing code and guidance, so the agent understands it produces actionable linking artifacts rather than pure state. It does not cover permissions, rate limits, or whether repeated calls rotate the pairing code, so a 4 rather than a 5.

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?

Three sentences with the usage rule front-loaded before the mechanics, and no redundant restatement of the title. Every sentence contributes either invocation guidance or return-value expectation.

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 zero-parameter tool with an output schema already present, the description supplies exactly the missing pieces: sequencing relative to siblings and the shape of the unlinked-state response. Nothing an agent needs in order to call it correctly is absent.

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?

The tool takes no parameters, so there is nothing for the description to disambiguate; the baseline for a zero-parameter tool applies. The description correctly conveys that the linking decision is driven entirely by server-side user state.

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?

Names a specific verb and resource — checks whether the user's phone is linked to WolfSMS — and goes on to state what it returns when the check fails. It is clearly distinguishable from list_devices and list_messages, which neither check linkage nor produce pairing artifacts.

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 an explicit ordering rule ('Call this first, before the other WolfSMS tools') with a stated exception ('unless you already know the user's phone is linked'). That is a when-to-use and when-to-skip rule in one sentence, leaving nothing to inference.

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