{"record":{"id":"7e9c56206e37f76a","repo":"googleapis/mcp-toolbox","slug":"looker-api-response-or-its-fields-object-is-nil","errorCode":null,"errorMessage":"looker API response or its fields object is nil","messagePattern":"looker API response or its fields object is nil","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"internal/tools/looker/lookercommon/lookercommon.go","lineNumber":105,"sourceCode":"\t\t\tif v.Suggestions != nil && len(*v.Suggestions) > 0 {\n\t\t\t\tvMap[\"suggestions\"] = *v.Suggestions\n\t\t\t}\n\t\t\tif v.SuggestExplore != nil && v.SuggestDimension != nil {\n\t\t\t\tvMap[\"suggest_explore\"] = *v.SuggestExplore\n\t\t\t\tvMap[\"suggest_dimension\"] = *v.SuggestDimension\n\t\t\t}\n\t\t}\n\t\tlogger.DebugContext(ctx, \"Converted to %v\\n\", vMap)\n\t\tdata = append(data, vMap)\n\t}\n\n\treturn data, nil\n}\n\n// CheckLookerExploreFields checks if the Fields object in LookmlModelExplore is nil before accessing its sub-fields.\nfunc CheckLookerExploreFields(resp *v4.LookmlModelExplore) error {\n\tif resp == nil || resp.Fields == nil {\n\t\treturn fmt.Errorf(\"looker API response or its fields object is nil\")\n\t}\n\treturn nil\n}\n\nfunc GetFieldParameters() parameters.Parameters {\n\tmodelParameter := parameters.NewStringParameter(\"model\", \"The model containing the explore.\")\n\texploreParameter := parameters.NewStringParameter(\"explore\", \"The explore containing the fields.\")\n\treturn parameters.Parameters{modelParameter, exploreParameter}\n}\n\nfunc GetQueryParameters() parameters.Parameters {\n\tmodelParameter := parameters.NewStringParameter(\"model\", \"The model containing the explore.\")\n\texploreParameter := parameters.NewStringParameter(\"explore\", \"The explore to be queried.\")\n\tfieldsParameter := parameters.NewArrayParameter(\"fields\",\n\t\t\"The fields to be retrieved.\",\n\t\tparameters.NewStringParameter(\"field\", \"A field to be returned in the query\"),\n\t)\n\tfiltersParameter := parameters.NewMapParameter(","sourceCodeStart":87,"sourceCodeEnd":123,"githubUrl":"https://github.com/googleapis/mcp-toolbox/blob/8cc6e09de2ad7b8bffc77751799585a1401a48eb/internal/tools/looker/lookercommon/lookercommon.go#L87-L123","documentation":"CheckLookerExploreFields is a nil-guard for the Looker API explore response: it verifies the LookmlModelExplore and its Fields object are non-nil before field extraction, because the Looker SDK can return partial responses where Fields is absent.","triggerScenarios":"Looker's GetExplore/lookml explore API returns a response whose Fields pointer is nil (explore not found, empty model, or API returning a stub object), then the tool calls this check before accessing resp.Fields.","commonSituations":"Querying a non-existent explore name/model; Looker instance returning malformed/partial data; SDK version changes altering response population; unauthenticated/limited-access explores.","solutions":["Verify the 'model' and 'explore' parameters match real explores in your Looker instance.","Check the Looker API credentials and permissions grant access to the explore.","Log/inspect the raw response to see why Fields was nil before retrying."],"exampleFix":"// before\nexplore, _ := sdk.GetLookmlModelExplore(ctx, model, exploreName)\nlookercommon.CheckLookerExploreFields(explore)\n// after\nexplore, err := sdk.GetLookmlModelExplore(ctx, model, exploreName)\nif err != nil { return err }\nif err := lookercommon.CheckLookerExploreFields(explore); err != nil {\n    return fmt.Errorf(\"explore %s/%s unavailable: %w\", model, exploreName, err)\n}\n","handlingStrategy":"type-guard","validationCode":"if explore == nil || explore.Fields == nil {\n    return fmt.Errorf(\"explore response incomplete\")\n}\n// then call CheckLookerExploreFields","typeGuard":"func hasExploreFields(resp *v4.LookmlModelExplore) bool {\n    return resp != nil && resp.Fields != nil\n}","tryCatchPattern":"if err := lookercommon.CheckLookerExploreFields(resp); err != nil {\n    // surface which model/explore failed and stop field extraction\n    return fmt.Errorf(\"explore %s/%s: %w\", model, exploreName, err)\n}","preventionTips":["Validate model/explore names against your Looker instance before invoking.","Check API errors from GetExplore before inspecting the response struct.","Ensure the Looker service account has access to the requested explore."],"tags":["looker","nil-check","api-response"],"backgroundTag":"nil-api-response","analyzedSha":"8cc6e09de2ad7b8bffc77751799585a1401a48eb","analyzedAt":"2026-09-05T01:10:36.887Z","contentChangedAt":"2026-09-05T01:10:36.887Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}