WhatsMCP: MCP for WhatsApp

Join Group

wa_join_group

Join a WhatsApp group from one of your accounts using its invite link.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`account_id`	Yes	the account to join from, as returned by wa_list_accounts
`invite_link`	Yes	the group invite link (https://chat.whatsapp.com/…) or bare code

Output Schema

TableJSON Schema

Name	Required	Description
`items`	No	the rows of a list operation
`status`	Yes	ok (the operation succeeded) or refused (see refusal; for wa_update_group, applied lists the changes that took effect before it)
`applied`	No	wa_update_group only: the settings that were changed, in order — on a refusal, the ones that took effect before it
`refusal`	No	present only when status is refused
`summary`	No	a human-readable result
`group_jid`	No	the new group's JID (wa_create_group only) — use it as wa_send_message's 'to'
`invite_link`	No	the group's invite link (wa_create_group or wa_get_group_invite_link)

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 22, 2026

addedOutput schema / properties / applied

Added value: +{
+  "description": "wa_update_group only: the settings that were changed, in order — on a refusal, the ones that took effect before it",
+  "items": {
+    "type": "string"
+  },
+  "type": [
+    "null",
+    "array"
+  ]
+}

changedOutput schema / properties / status / description

Previous value: -"ok (the operation succeeded) or refused (nothing was done)"New value: +"ok (the operation succeeded) or refused (see refusal; for wa_update_group, applied lists the changes that took effect before it)"

First observedSep 17, 2026

TDQS

A3.8/5.0

Behavior3/5

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

Annotations already indicate a non-read-only, non-idempotent, non-destructive action, and the description does not contradict them. It adds little beyond the annotations—no mention of failure behavior, account pairing requirements, or membership side effects—but the action is simple and the safety profile is covered.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single front-loaded sentence with no filler. Every phrase adds meaningful context: joining, account selection, and the invite-link mechanism.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple two-parameter operation with full schema coverage, an output schema, and annotation coverage, the description is largely complete. It could mention expected success/failure behavior, but nothing critical is missing for an agent to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with both parameters fully documented. The description restates 'invite link' and 'one of your accounts' but does not add meaning beyond what the schema already provides, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('Join'), a resource ('WhatsApp group'), and the mechanism ('using its invite link'), along with the account context. It is clearly distinguishable from siblings like wa_create_group and wa_leave_chat, even without naming them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies the tool is for joining an existing group via an invite link, but it gives no explicit when-to-use or when-not-to-use guidance versus alternatives such as wa_create_group or wa_leave_chat. Context is present, but exclusions are missing.

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

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