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WhatsMCP: MCP for WhatsApp

by com.whatsmcp.app
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Join Group

wa_join_group

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

Input Schema

NameRequiredDescriptionDefault
account_idYesthe account to join from, as returned by wa_list_accounts
invite_linkYesthe group invite link (https://chat.whatsapp.com/…) or bare code

Output Schema

NameRequiredDescriptionDefault
itemsNothe rows of a list operation
statusYesok (the operation succeeded) or refused (see refusal; for wa_update_group, applied lists the changes that took effect before it)
appliedNowa_update_group only: the settings that were changed, in order — on a refusal, the ones that took effect before it
refusalNopresent only when status is refused
summaryNoa human-readable result
group_jidNothe new group's JID (wa_create_group only) — use it as wa_send_message's 'to'
invite_linkNothe group's invite link (wa_create_group or wa_get_group_invite_link)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedOutput schema / properties / refusal / properties / candidates
      Added value: +{
+  "description": "on an account_ambiguous refusal: the accounts to choose from — retry with one of these as account_id",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "account_id": {
+        "description": "the id to retry with as account_id",
+        "type": "string"
+      },
+      "name": {
+        "description": "the account's WhatsApp display name",
+        "type": "string"
+      },
+      "phone": {
+        "description": "the account's phone number, E.164",
+        "type": "string"
+      },
+      "status": {
+        "description": "whether the number works right now — live, connecting, or why not, as wa_list_accounts reports it",
+        "type": "string"
+      }
+    },
+    "required": [
+      "account_id"
+    ],
+    "type": "object"
+  },
+  "type": [
+    "null",
+    "array"
+  ]
+}
  2. Changed3 schema fields changed
    • addedOutput schema / properties / refusal / properties / account_status
      Added value: +{
+  "description": "when the number is not working: its status — starting, not_running, whatsapp_down, suspended, pairing, unlinked or locked",
+  "type": "string"
+}
    • addedOutput schema / properties / refusal / properties / account_status_reason
      Added value: +{
+  "description": "the detail of account_status, e.g. no_egress, stopped, no_plan",
+  "type": "string"
+}
    • addedOutput schema / properties / refusal / properties / since
      Added value: +{
+  "description": "when the number stopped working, RFC3339, when known",
+  "type": "string"
+}
  3. Changed2 schema fields changed
    • 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)"
  4. First observed

TDQS

C2.9/5.0
Behavior2/5

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

Annotations already declare readOnly=false, idempotent=false, destructive=false, so the safety profile is covered; the description adds only the invite-link mechanism, which is already a parameter. It says nothing about what happens if the account is already a member, if the link is expired, or whether admin approval is required — meaningful gaps for a non-idempotent mutation.

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

Conciseness4/5

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

A single well-formed sentence with the action front-loaded and zero filler. There is little structure to speak of, but nothing is wasted.

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

Completeness3/5

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

An output schema exists so return values need not be explained, and both required params are described in the schema. However, for a non-idempotent write operation with group-membership side effects, the description omits failure and idempotency behavior the agent would need to call it confidently.

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%, and both parameters (account_id via wa_list_accounts, invite_link accepting either a full URL or bare code) are fully documented there. The description adds no meaning beyond that, so baseline 3 applies.

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

Purpose4/5

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

States a specific verb+resource ('Join a WhatsApp group') plus scope ('from one of your accounts') and mechanism ('using its invite link'), which cleanly separates it from wa_create_group and wa_get_group_invite_link. It stops short of naming any sibling explicitly, so it lands at 4 rather than 5.

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

Usage Guidelines2/5

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

No guidance on when to use this versus wa_create_group, wa_update_group, or wa_follow_channel, and no exclusions or prerequisites. The agent must infer usage from the verb alone.

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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