Vapi MCP Server

Instructions

Implementation Reference

• src/tools/call.ts:40-43 (handler)

  Core handler logic: fetches call details by ID using Vapi client and transforms output.

  createToolHandler(async (data) => {
    const call = await vapiClient.calls.get(data.callId);
    return transformCallOutput(call);
  })

• src/schemas/index.ts:303-305 (schema)

  Zod schema defining input for get_call: requires 'callId' as string.

  export const GetCallInputSchema = z.object({
    callId: z.string().describe('ID of the call to get'),
  });

• src/tools/call.ts:36-44 (registration)

  Registers the 'get_call' tool with MCP server, including name, description, input schema, and handler.

  server.tool(
    'get_call',
    'Gets details of a specific call',
    GetCallInputSchema.shape,
    createToolHandler(async (data) => {
      const call = await vapiClient.calls.get(data.callId);
      return transformCallOutput(call);
    })
  );

• src/tools/utils.ts:30-41 (helper)

  Helper that wraps raw handler functions with try-catch error handling and standardizes response format.

  export function createToolHandler<T>(
    handler: (params: T) => Promise<any>
  ): (params: T) => Promise<ToolResponse> {
    return async (params: T) => {
      try {
        const result = await handler(params);
        return createSuccessResponse(result);
      } catch (error) {
        return createErrorResponse(error);
      }
    };
  }

• src/transformers/index.ts:211-229 (helper)

  Transformer utility that converts Vapi Call object to the standardized CallOutputSchema.

  export function transformCallOutput(
    call: Vapi.Call
  ): z.infer<typeof CallOutputSchema> {
    return {
      id: call.id,
      createdAt: call.createdAt,
      updatedAt: call.updatedAt,
      status: call.status || '',
      endedReason: call.endedReason,
      assistantId: call.assistantId,
      phoneNumberId: call.phoneNumberId,
      customer: call.customer
        ? {
            number: call.customer.number || '',
          }
        : undefined,
      scheduledAt: call.schedulePlan?.earliestAt,
    };
  }