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luiso2

Evolution API WhatsApp MCP Server

by luiso2

list_instances

Retrieve all active WhatsApp Business instances to manage messaging accounts, monitor connection status, and organize communication channels.

Instructions

List all WhatsApp instances

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • The handler function for the 'list_instances' tool. It fetches the list of WhatsApp instances from the EvolutionAPI service and returns them as a JSON-formatted text content block.
    private async handleListInstances() {
      const instances = await evolutionAPI.fetchInstances();
      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify(instances, null, 2)
          }
        ]
      };
    }
  • src/index.ts:56-63 (registration)
    The tool registration definition including name, description, and empty input schema (no parameters required). This is part of the tools array registered with the MCP server.
    {
      name: 'list_instances',
      description: 'List all WhatsApp instances',
      inputSchema: {
        type: 'object',
        properties: {}
      }
    },
  • The input schema for the 'list_instances' tool, which requires no parameters.
    inputSchema: {
      type: 'object',
      properties: {}
    }
  • Supporting helper method in EvolutionAPI service that performs the actual HTTP GET request to the Evolution API endpoint '/instance/fetchInstances' to retrieve the list of instances.
    async fetchInstances(): Promise<Instance[]> {
      const response = await this.client.get('/instance/fetchInstances');
      return response.data;
    }
Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. 'List all WhatsApp instances' implies a read-only operation, but it doesn't specify whether this requires authentication, returns paginated results, includes inactive instances, or has rate limits. For a tool with zero annotation coverage, this leaves significant gaps in understanding its 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 with zero wasted words. It is front-loaded with the core action ('List all WhatsApp instances'), making it easy to parse. Every word earns its place by conveying essential information without redundancy.

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?

Given the tool's simplicity (0 parameters, no output schema, no annotations), the description is minimally adequate. It states what the tool does but lacks context about behavior, output format, or usage scenarios. For a listing tool with no structured metadata, more detail on return values or constraints would improve completeness.

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

Parameters4/5

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

The tool has 0 parameters, and schema description coverage is 100%, so there are no parameters to document. The description doesn't need to add parameter semantics, and it correctly doesn't mention any. A baseline of 4 is appropriate for a parameterless tool with complete schema coverage.

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 'List all WhatsApp instances' clearly states the verb ('List') and resource ('WhatsApp instances'), making the tool's purpose immediately understandable. It distinguishes from siblings like 'instance_status' (which checks status) or 'create_instance' (which creates). However, it doesn't specify scope or filtering details that might differentiate it from similar listing tools.

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 an active connection), exclusions (e.g., not for filtered lists), or comparisons to siblings like 'get_chats' or 'list_contacts'. The agent must infer usage from the tool name 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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