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

Annotations already declare readOnlyHint=false and destructiveHint=true, so safety profile is known. The description adds useful behavioral context beyond annotations: it clarifies 'No WhatsApp Business account is involved' and states the side effect 'unlocks agents messaging the owner.' No contradiction with 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?

Two sentences, front-loaded with the core action, then purpose and an important instruction. Every sentence earns its place; no redundancy or fluff.

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 simple action with two parameters (both fully schema-described) and no output schema, the description covers the trigger context, the required input (owner's own number), and the consequences (unlocks agents). Missing details like rate limits or next steps are minor and not essential for calling this tool correctly.

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 coverage is 100%, so both parameters are documented. The description adds procedural guidance for the phone parameter ('Ask the user for their own WhatsApp number first and send only to that'), which clarifies how the agent should obtain and use the value. This goes beyond the schema's format hint.

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+resource: 'Send a 6-digit code over WhatsApp to the ACCOUNT OWNER's own phone.' It also explains the broader purpose (ownership proof required before platform number connection) and adds context about unlocking agent messaging. While it doesn't name sibling tools, the action is unambiguous and clearly distinct from confirmation steps like confirm_owner_phone_verification.

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 clear usage context: 'one-time ownership proof required before a platform number can be connected' and 'unlocks agents messaging the owner.' This implies when to use it, though it doesn't explicitly name alternatives or exclusions (e.g., 'use confirm_owner_phone_verification after').

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