WorkflowRuleBatch finds all workflow rule names, then uses Andrew Fawcett's MetadataService to query for additional details

WorkflowRuleBatch.java

global class WorkflowRuleBatchable implements Database.Batchable<String>, Database.AllowsCallouts, Database.Stateful
{
    global final List<MetadataService.WorkflowRule> wfrs;
    private final String sessionId;
    
    global WorkflowRuleBatchable(String sessionId)
    {
        this.sessionId = sessionId;
        wfrs = new List<MetadataService.WorkflowRule>();
    }
    
    global List<String> start(Database.BatchableContext bc)
    {
        String salesforceHost = System.Url.getSalesforceBaseURL().toExternalForm();
        String urlHost = salesforceHost + '/services/data/v30.0/tooling/query/?q=Select+Id+,Name,+TableEnumOrId+from+WorkflowRule';
        
        HTTPResponse res = metadataQuery(urlHost);
        
        //system.debug('workflow res = ' + res);
        //system.debug('workflow res.getBody() = ' + res.getBody());
        List<String> workflowRuleNames = new List<String>();
        
        WorkflowRule wfrs = (WorkflowRule) System.JSON.deserialize(res.getBody(), WorkflowRule.class);
        
        for(Integer j=0; j < wfrs.records.size(); j++ )
        {
            String fullName = wfrs.records[j].TableEnumOrId + '.' + wfrs.records[j].Name;
            workflowRuleNames.add(fullName);
        }
        return workflowRuleNames;
    }
    
    global void execute(Database.BatchableContext bc, List<String> scope)
    {
        MetadataService.MetadataPort service = new MetadataService.MetadataPort();
        service.SessionHeader = new MetadataService.SessionHeader_element();
        service.SessionHeader.sessionId = this.sessionId;
        
        // Read Workflow Alert		
        MetadataService.WorkflowRule wfr = (MetadataService.WorkflowRule) service.readMetadata('WorkflowRule', scope).getRecords()[0];
        wfrs.add(wfr);
    }
    
    global void finish(Database.BatchableContext bc)
    {
        system.debug('wfrs = ' + wfrs);
    }
    
    HTTPResponse metadataQuery(String urlHostVariable)
    {
        HttpRequest req = new HttpRequest();
    
        req.setMethod('GET');
        req.setEndpoint(urlHostVariable);
        req.setHeader('Content-type', 'application/json');
        req.setHeader('Authorization', 'Bearer ' + this.sessionId);
        Http http = new Http();
       
        return http.send(req);
    }
    
    class WorkflowRule 
    {
        public Integer size;
        public Integer totalSize;
        public Boolean done;
        public Object queryLocator;
        public String entityTypeName;
        public List<Records> records;
        
            public WorkflowRule(Integer size, Integer totalSize, Boolean done, Object queryLocator, String entityTypeName, List<Records> records)
            {
                this.size = size;
                this.totalSize = totalSize;
                this.done = done;
                this.queryLocator = queryLocator;
                this.entityTypeName = entityTypeName;
                this.records = records;
            }
    }
    class Attributes 
    {
        public String type;
        public String url;
    }
    class Records 
    {
        public Attributes attributes;
        public String Id;
        public String Name;
        public String TableEnumOrId;
        
            public Records(Attributes attributes, String Id, String Name, String TableEnumOrId)
            {
                this.attributes = attributes;
                this.Id = Id;
                This.Name = Name;
                this.TableEnumOrId = TableEnumOrId;
            }
    }
}