List allowed WhatsApp chats

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

With readOnlyHint=true already covering the read-only nature, the description adds useful behavioral detail: the exact fields returned (including canPost) and a 'lightweight recent-activity count,' plus a guarantee about scope. This goes beyond the annotation without contradicting it. No side effects or caveats need disclosure for a read-only list tool.

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 with no redundant words. The primary action and outcome come first, followed by a compact enumeration of returned fields. The final exclusion sentence earns its place by removing ambiguity about scope.

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 parameterless read-only list operation, the description fully covers what an agent needs to know to call it correctly: what it returns (fields) and its scope (allowed chats only). No output schema exists, but the description compensates by naming all returned fields. Absent pagination or sorting requirements are not significant for such a lightweight operation.

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 takes zero parameters and schema coverage is 100%, so there is no parameter information to add. The description does not need to explain inputs, and the baseline of 4 for a no-parameter tool is appropriate.

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 uses a specific verb (Lists) and resource (WhatsApp chats this server may touch), and names the exact fields returned: jid, display name, canPost, and recent-activity count. The scope restriction 'Never lists any other chat' further distinguishes it from siblings like read_chat_messages or send_chat_message, which operate on individual chats.

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 implies when to use the tool: to discover which WhatsApp chats are available for interaction on this server. The phrase 'this server may touch' sets expectations about scoping, and 'Never lists any other chat' is an exclusion. However, it does not explicitly compare against sibling tools or state when not to use it, so it falls just short of a 5.

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