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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, and the description adds substantive context beyond them: the credential is single-use and temporary, the operation neither disconnects a phone nor sends gameplay input, and the QR must never be published. That is exactly the extra behavioral disclosure a safety-sensitive tool needs.

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?

Front-loads the core action and follows with prerequisites, defaults, and safety constraints in a logical order. Slightly dense and fragmented by ellipses, and the network requirement could be merged into the prerequisites sentence, but nearly every clause earns its place.

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 one-optional-param, read-only tool with annotations and no output schema, this covers preconditions, multi-device selection, network constraints, and safety. The remaining gap is QR lifetime/expiry behavior and what the caller should do if pairing fails, which are not addressed.

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 0% and the receiverId pattern is only in the schema, so the description must carry the meaning. It does explain what receiverId selects (a specific sharing Mac/receiver) and when to ask the user for it, though it never describes the identifier's form or how to obtain a valid value beyond the in-app Pair menu.

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 and resource (display a single-use pairing QR image inline in ChatGPT) plus the exact scope of what it returns. It is unmistakably distinct from siblings like list_devices, delivery_status, or profile_schema, and an agent can route to it without opening the schema.

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 explicit preconditions (Mac owner must choose Pair in the receiver menu and sign in to the same account), the default call pattern (no arguments for one sharing Mac), and the branch for multiple Macs (ask the user which receiverId). It also names the environmental requirement that both devices share local Wi-Fi.

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