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

No annotations are provided, so the description carries the behavioral disclosure burden. It usefully notes that blocking controls message reception and that contacts are identified by phone number rather than WhatsApp ID, but it omits permissions, reversibility, side effects on existing chats, and response behavior for a mutation tool.

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 short and front-loaded, with the core purpose stated immediately. It has some redundancy between 'blocking and unblocking operations' and 'contact blocking status,' but it remains efficient.

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 three-parameter mutation tool with full schema coverage, the description covers purpose and identifier format adequately. However, without annotations or an output schema, it should say more about operational effects, permissions, and whether blocking changes existing conversations.

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 100%, so the schema already documents action, device, and contacts. The description reinforces E.164 formatting and clarifies that contacts are not identified by WhatsApp ID, but adds no meaning beyond the schema for device or action 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 states a clear resource and operation: WhatsApp contact blocking and unblocking, with action-based control over message reception. It is more specific than the bare tool name, though it does not explicitly contrast itself with sibling tools like manage_whatsapp_contacts.

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?

The description implies usage by explaining that the tool controls message reception from specific contacts, but it does not state when to use this tool versus manage_whatsapp_contacts or provide any exclusions or prerequisites.

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