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

With no annotations to lean on, the description still discloses real behavioral traits: the 30-day lookback window for delivery_status, the 20-ID batch cap, auto-selection/error semantics for device, and that maxMessages is paginated under the hood. It omits auth requirements and whether 'export' produces inline content vs. a downloadable file artifact.

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?

Front-loaded summary sentence followed by a scannable action list and a dedicated paragraph for the tricky device parameter. Minor redundancy: the device paragraph largely repeats the schema's description of accepted ID formats, though it adds the error-handling behavior.

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?

Ten parameters with no output schema and no annotations mean the description must carry a lot, and it covers actions, key constraints, and the device parameter well. It never explains what an 'export' returns (inline payload, file reference, or link) or which parameters apply to which action, which matters given the shared schema.

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%, so baseline is 3; the description earns above that by encoding conditional requirements the schema cannot express (chat required for export, messageIds required for delivery_status) and by restating the device identifier formats alongside their fallback behavior.

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 resource (WhatsApp chat messages) and enumerates the two actions it performs (delivery_status, export), so the agent knows exactly what capability is offered. It does not, however, differentiate itself from close siblings such as export_whatsapp_chats or get_whatsapp_chat_messages, leaving overlap ambiguous.

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?

Gives action-level guidance (delivery_status for outbound receipts, export for dumping messages) and states the device auto-selection rule with the exact failure behavior ('errors with the list of available devices so you can ask the user'). It stops short of saying when to pick this tool over the sibling export/list tools.

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