Poll for new WhatsApp messages

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

Annotations provided readOnlyHint=true, and the description adds valuable behavioral detail: it drains only new messages, groups them by chat jid, persists the read position, and guarantees each message is returned exactly once. This goes beyond the annotation without contradicting it.

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, no filler, with the core action and grouping front-loaded. The second sentence adds the important delivery guarantee without redundancy.

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 no-parameter polling tool, the description covers purpose, grouping, and delivery semantics. It does not describe the exact response shape or empty-result behavior, but the absence of an output schema and simple tool complexity make this acceptable.

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?

Tool has zero parameters, so baseline is 4. Description confirms no input is needed and explains the semantics of the poll position, which is the only relevant 'parameter-like' state.

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?

Description uses a specific verb ('Drains') and resource ('messages that arrived since the last poll_chats call'), and specifies grouping by chat jid. It is clearly distinguishable from siblings list_chats, read_chat_messages, and send_chat_message.

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 description clearly establishes the polling pattern: it returns messages that arrived since the previous poll_chats call, and the persisted read position implies it is meant for repeated incremental fetching. It does not explicitly name alternatives or exclusions, but the usage context is clear.

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