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sawa-zen

VRChat MCP Server

vrchat_join_group

Join a VRChat group using its unique group ID to access community features and connect with members.

Instructions

Join a VRChat group by ID

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
groupIdYesMust be a valid group ID

Implementation Reference

  • The async handler function that authenticates the VRChat client, joins the specified group using groupsApi.joinGroup, and returns the JSON response or an error message.
    async (args) => {
      try {
        await vrchatClient.auth()
        const response = await vrchatClient.groupsApi.joinGroup(args.groupId)
        return {
          content: [{
            type: 'text',
            text: JSON.stringify(response.data, null, 2)
          }]
        }
      } catch (error) {
        return {
          content: [{
            type: 'text',
            text: 'Failed to join group: ' + error
          }]
        }
      }
    }
  • Zod input schema defining the required 'groupId' parameter as a string.
    {
      groupId: z.string().describe('Must be a valid group ID')
    },
  • Direct registration of the 'vrchat_join_group' tool on the MCP server, including description, input schema, and inline handler.
      'vrchat_join_group',
      'Join a VRChat group by ID',
      {
        groupId: z.string().describe('Must be a valid group ID')
      },
      async (args) => {
        try {
          await vrchatClient.auth()
          const response = await vrchatClient.groupsApi.joinGroup(args.groupId)
          return {
            content: [{
              type: 'text',
              text: JSON.stringify(response.data, null, 2)
            }]
          }
        } catch (error) {
          return {
            content: [{
              type: 'text',
              text: 'Failed to join group: ' + error
            }]
          }
        }
      }
    )
  • src/main.ts:34-34 (registration)
    Invocation of createGroupsTools in the main server setup, which registers the vrchat_join_group tool among others.
    createGroupsTools(server, vrchatClient)
Behavior2/5

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

With no annotations provided, the description carries full burden for behavioral disclosure. It states the action ('Join') but doesn't explain what this entails—whether it requires user permissions, sends notifications, has rate limits, or what happens on success/failure. This leaves significant gaps for an AI agent to understand the tool's behavior.

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, efficient sentence that directly states the tool's purpose without unnecessary words. It's front-loaded with the core action and resource, making it easy to parse quickly.

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

Completeness2/5

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

Given the tool's complexity (a write operation to join a group), lack of annotations, and no output schema, the description is insufficient. It doesn't cover behavioral aspects like authentication needs, error conditions, or return values, leaving the AI agent with incomplete context for safe and effective use.

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?

The input schema has 100% description coverage, with the single parameter 'groupId' documented as 'Must be a valid group ID'. The description adds no additional semantic context beyond this, such as where to obtain group IDs or format examples. Baseline 3 is appropriate since the schema already provides adequate parameter documentation.

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?

The description clearly states the action ('Join') and target resource ('a VRChat group by ID'), making the purpose immediately understandable. However, it doesn't differentiate this tool from potential alternatives like 'vrchat_request_invite' or 'vrchat_send_friend_request' which might also involve joining or connecting to entities in VRChat.

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?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., needing authentication, being a VRChat user), exclusions (e.g., cannot join private groups), or when to choose other tools like 'vrchat_search_groups' first to find group IDs.

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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