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

The description goes well beyond the annotations by disclosing that the tool returns immediately, that a first sync can take minutes, that waiting previously caused the sync to be killed by a timeout, and that read tools trigger background syncs causing potential staleness. It also flags the use of an unofficial Wacli client and the risk of account restriction, providing rich behavioral context.

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?

The description is dense but every sentence earns its place: it states the core behavior, explains the timeout issue, names the diagnostic sibling, warns about background syncs, and notes the third-party risk. The most important information is front-loaded, and the warning is clearly marked.

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 zero-parameter tool with an output schema, the description is complete. It covers what the tool does, the asynchronous behavior, how to check status, the staleness caveat, and the risk of using an unofficial client. The reference to 'after linking' implies the prerequisite of connecting WhatsApp, which is sufficient given the sibling whatsapp_connect tool.

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?

The tool has zero parameters and the schema description coverage is 100%, so there are no parameter semantics to clarify. The description still adds context about what is synced (messages, groups, contacts), which is useful even though it is not parameter-specific.

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 clearly states the tool's action: 'Starts WhatsApp pulling the latest messages, groups and contacts into the local store' and emphasizes that it returns immediately without waiting. It also distinguishes itself from related read tools by explaining that they trigger background syncs, and it names whatsapp_diagnose as the status-check sibling.

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 gives explicit guidance to call whatsapp_diagnose to check sync status, and warns that other read tools kick off background syncs so first reads may be stale. It does not explicitly say 'use this tool when you want to force a sync' versus relying on read tools, but the context strongly implies the appropriate use.

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