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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context by disclosing pagination via limit/after and that the response carries next_cursor, which tells the agent it must loop to see all blocked numbers.

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?

A single front-loaded sentence with the resource named first and pagination second; nothing is wasted. The nested parenthetical around wa_id and next_cursor slightly crowds the sentence but costs no clarity.

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 read-only list tool with no output schema, the description plus annotations supply everything needed: scope, safety profile, and the pagination contract including the cursor handoff. Only auth/permission requirements and empty-result behavior are unstated, which is a minor gap.

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 75% and 'after' already documents the next_cursor linkage, so the description largely restates structured data. It does tie limit/after together as a pagination pair, but adds no format or range detail beyond the schema; baseline 3 is appropriate.

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 (List) plus the exact resource (phone numbers / wa_id blocked on a WhatsApp phone number), which cleanly separates it from the write siblings whatsapp_users_block and whatsapp_users_unblock. An agent can identify this as the read/list operation 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?

The description never says when to reach for this tool instead of siblings like whatsapp_blocked_user_status (single-number status check) or whatsapp_users_block. Usage is only implied by the listing nature of the verb; no alternatives or preconditions are named.

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