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

Beyond the annotations (readOnlyHint, openWorldHint, destructiveHint), the description discloses that the tool uses an unofficial client (Wacli) and that accounts may be restricted for ToS violations. This is critical behavioral context not present in annotations, and it does not contradict them. It also reinforces the JID origin constraint.

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: the first delivers the core function, the second covers the critical constraint and a risk. It is front-loaded, efficient, and every sentence earns its place without 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 single-parameter read-only tool with an output schema, the description covers the purpose, the source of the input, and a key risk. There is an output schema so return format need not be explained. Nothing an agent needs to call it correctly is missing.

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% and already explains group_jid as a group JID from whatsapp_list_groups. The description repeats this and adds the warning not to fabricate it, but that's more of a usage caution than new semantic information. The baseline of 3 is appropriate since the schema carries the parameter meaning.

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 specific action ('Fetches') and resource ('WhatsApp group's live info + participant list'), clearly distinguishing it from siblings like whatsapp_list_groups (which lists groups) and whatsapp_read_messages. It immediately tells the agent what the tool does and its scope.

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?

It gives a clear prerequisite: group_jid must come from whatsapp_list_groups and never be fabricated. This tells the agent when to use the tool (after listing groups) and warns against guessing. It doesn't explicitly mention alternatives, but the context is sufficient for correct selection.

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