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

The annotations already declare the non-read-only and non-idempotent nature, and the description adds useful behavioral constraints about conflicting tools and the returned pairing code. It does not cover code expiration or the full session-state effect, so it is strong but not exhaustive.

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 front-loaded with the purpose and return value, then adds usage constraints with no unnecessary text. Every sentence adds actionable information.

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?

It explains the return value and critical sibling conflicts, which makes the tool callable in context. The main remaining gap is the required phone_number parameter semantics, which are not covered by the schema or description.

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 schema has 0% description coverage for phone_number, and the description only indirectly implies it is the phone to link. It does not specify expected format, country code, or whether it must be the WhatsApp account number.

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 states a specific action and outcome: it initiates pairing and returns an 8-character code. It also distinguishes this tool from the sibling get_pairing_qr by naming the alternative pairing method.

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 explicitly says when to use this tool (best when the user is on the phone they want to link), names the alternative method, and states hard exclusions: never call it with get_pairing_qr and never call restart_session during pairing.

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