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

Beyond the annotations (readOnly=false, openWorld=true, destructive=false), the description reveals important behaviors: a QR code is displayed in the chat, linking is one-account-at-a-time, disconnect must precede switching accounts, and an already-linked invocation simply reports status. This is exactly the kind of side-effect and statefulness context that annotations alone don't convey.

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 front-loads the purpose and then adds only essential operational details: phone steps, post-link behavior, account constraint, and idempotent already-linked result. Each sentence contributes a distinct fact, and the reader gets a complete mental model without 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 zero-parameter connection tool with an output schema present, the description is nearly complete: it specifies how to trigger the flow, what the user must do on the phone, what changes after success, and the one-account constraint. It could add failure/timeout behavior, but the output schema covers return semantics, and the core invocation knowledge is present.

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 input schema is empty (0 parameters, 100% schema coverage), so there are no parameter meanings to clarify. The baseline for zero-parameter tools is 4, and the description appropriately focuses on the user-facing linking steps rather than parameters.

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 opens with a specific verb and resource: 'Link WhatsApp to Local MCP by showing a QR code right here in the chat — no Terminal needed.' This clearly distinguishes the tool from WhatsApp messaging/search siblings by focusing on the connection/linking action, and the mechanism (QR scan) makes it unmistakable.

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 provides the invocation context: call this before WhatsApp tools are usable, follow the phone-side QR scan steps, and it handles the already-linked case by reporting it. It names one explicit ordering rule ('to switch to a different account, run whatsapp_disconnect first'), but it doesn't explicitly direct agents away from alternative connection/diagnostic tools in ordinary situations.

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