Join a WhatsApp group from an invite

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

The description goes well beyond the annotations by explaining the preview behavior ("Without confirm: true it joins nothing"), the visible side effect ("Every member sees the account join"), and the pending_approval result. This is particularly valuable because idempotentHint: false and readOnlyHint: false leave behavioral details unexplained without extra 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 detailed but every sentence earns its place: the invite formats, the confirm condition, the return values, and the visible side effect are all stated without redundancy or filler. The structure is front-loaded with the core mechanics before the confirmation instructions.

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 4-parameter two-phase tool with no output schema, the description is complete: it defines the inputs, the preview response fields, the confirmed response (chat_id or pending_approval), and the side effect of joining. An agent has enough context to call the tool correctly and interpret its result.

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 baseline is 3, but the description adds meaningful parameter semantics beyond the schema: it clarifies the exact-one-of requirement for invite/message_id and distinguishes the preview call from the confirm call. This extra guidance justifies a 4.

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 action as "Join a group from an invite" and specifies the accepted invite forms (link or code, or invite message_id), which distinguishes it from sibling tools like create_group, get_group_info, and manage_group. The title and description together convey the exact scope of the operation without ambiguity.

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?

It gives explicit invocation guidance: exactly one of invite / message_id must be supplied, and the two-phase confirm flow is described step by step (preview without confirm: true, then call again with confirm: true after user consent). It does not explicitly name alternative tools or exclusions, but provides clear context for when this tool should be used.

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