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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile of this read query is fully covered. The description adds no further behavioral context such as required permissions, rate limits, or what a positive/negative result means. With annotations carrying the load, this is an acceptable 3.

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 no redundant clauses or filler. The scope qualifier ('one phone number') is placed immediately, so every word earns its place.

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, fully-annotated, read-only boolean check with 100% schema coverage and no output schema, the description is nearly sufficient. The only minor gap is that it does not clarify the return shape, though a yes/no status query strongly implies the answer and no output schema is defined.

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%; each of the three parameters (user, profile_id, phone_number_id) is documented in the schema itself. The description adds no syntax, format, or identifier guidance beyond what the schema already provides, 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?

The description uses a specific verb ('Check') and resource ('whether one phone number is currently blocked'), so intent is unambiguous. It implies a single-number scope ('one phone number') that distinguishes it from whatsapp_blocked_users_list, but it never names that sibling explicitly, so differentiation is implicit rather than stated.

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?

There is no when-to-use or when-not-to-use guidance. The description does not mention the related whatsapp_blocked_users_list (for enumerating all blocked users) or whatsapp_users_block/unblock (for changing block state), so an agent gets no routing help among these closely related siblings.

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