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

Annotations already establish readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavioral detail beyond that: the return payload is a bare array of {id, consumer_phone_number} with no `data` wrapper, which prevents a common parsing mistake.

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, both load-bearing and front-loaded: the primary behavior first, then the return-shape caveat. No filler or restatement of the title.

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?

With no output schema, the description correctly compensates by disclosing the return structure, and the single required parameter is fully documented in schema. Pagination or empty-list behavior is unmentioned, but for a simple read tool this is close to sufficient.

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?

Only one parameter exists and schema description coverage is 100%, with the schema explaining that app_id identifies the channel's WhatsApp number. The description adds nothing about the parameter, so the baseline 3 applies.

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?

Names a specific verb and resource ('List the consumer phone numbers allowed to reach the agent') and scopes it to the ALLOWLISTED_ONLY audience mode. An agent can readily distinguish it from mba_add_allowlist_entry and mba_remove_allowlist_entry, though those siblings are not named explicitly.

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 when the tool is relevant by tying it to 'while ai_audience is ALLOWLISTED_ONLY', which is useful context. It does not explicitly say when not to use it or direct the caller to the add/remove siblings for mutation, leaving routing partly to inference from tool names.

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