whatsmcp

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.

Changed3 schema fields changedOct 14, 2026

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"
+}

First observedSep 27, 2026

TDQS

B3.3/5.0

Behavior2/5

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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond that: no note on what happens if the account is already a member, whether the link can expire, or any rate limiting, leaving the behavioral burden on structured fields.

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?

A single 14-word sentence with the action, target, source account and required input all front-loaded. Nothing is wasted and nothing needs to be skimmed for.

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 this is a simple two-parameter mutation whose inputs are fully documented in the schema. What is missing is failure/edge-case context (already a member, invalid or expired link) that an agent would want before invoking a non-idempotent join.

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 coverage is 100%, and both properties carry their own descriptions including the account lookup chain ('as returned by wa_list_accounts') and the accepted invite-link format. The description adds no parameter detail beyond the schema, so the 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 ('Join') and resource ('WhatsApp group') plus the mechanism ('using its invite link'), which separates it from wa_create_group and wa_leave_chat. It does not explicitly name a sibling it could be confused with, but the purpose is unambiguous.

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?

Usage is implied rather than stated: the 'using its invite link' phrase tells the agent an invite link is required, which quietly routes it away from groups it already belongs to. There is no explicit when-to-use/when-not guidance or pointer to alternatives such as wa_get_group_invite_link or wa_list_groups.

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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