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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description contributes genuine domain behavior — the 24-hour window rule and the template-only constraint outside it — but says nothing about the shape of the answer (boolean vs. expiry timestamp) or what happens for contacts with no WhatsApp number.

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 short sentences with zero padding, and the operative concept (whether the window is open) is front-loaded ahead of the consequence.

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 with full schema coverage and safety annotations, the definition is largely sufficient. However, with no output schema, the agent is left guessing whether the result is a boolean, a timestamp of expiry, or a richer object, which matters for deciding whether it can still send a free-form message.

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 baseline is 3. The description adds no guidance on choosing between the 'from' and 'number' parameters when a workspace or contact has multiple WhatsApp numbers, which is the only non-obvious selection decision here.

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 names the specific resource — a contact's 24-hour WhatsApp customer-service window — and states exactly what it reports ('whether ... is open'). Unlike the many send/list/get siblings, it clearly reads as a status check, though it never contrasts itself with alternatives such as desk_lookup_contact or the WhatsApp send tools.

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?

Usage is implied rather than stated: the note that 'outside it only an approved template can be sent' hints this should be checked before sending free-form WhatsApp messages, but no sibling tool (e.g. desk_send_message, send_whatsapp_message, desk_list_templates) is named and no explicit 'call this before X' instruction is given.

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