whatsapp_request_chat_messages

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

Discloses behavior the annotations cannot convey: the call does NOT return messages, the actual messages arrive asynchronously as history-sync events, and they only arrive 'if the phone provides them'. This is exactly the context an agent needs to avoid mis-handling the acknowledgement as a result set.

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?

Three short sentences, front-loaded with the action, then the async caveat, then the return shape. Nothing is padded and the most surprising fact (no messages returned) is stated early.

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?

There is no output schema, so the description carries the return-value burden — and it does so explicitly ('Returns an acknowledgement only'), while also explaining the real delivery channel. An agent has everything needed to call it and interpret the response.

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 the schema already documents count, chatId, lastMessageId and lastMessageSenderId. The description adds only the 'starting before' framing for the anchor, which is marginal value over structured data. 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?

States a specific verb and resource ('Ask WhatsApp for older messages of a chat') plus the exact anchor point ('starting before a given message'). No sibling tool performs history backfill, so it is unambiguously distinguishable from the get/send/mutate siblings.

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 context for use is clear: recover older messages of a known chat when you have a last-known message reference. It does not name any alternative sibling or state exclusions, but no sibling competes for this job, so the gap is minor.

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