1. A method of operating a computer system comprising: accessing a library of mashup application performance monitors that are part of a mashup application runtime environment of a mashup application development environment; analyzing a mashup application that is being created in the mashup application development environment relative to the mashup application performance monitors in the library of mashup application performance monitors; identifying matching ones of the mashup application performance monitors that are applicable to the mashup application that is being created in the mashup application development environment, responsive to the analyzing; presenting the matching ones of the mashup application performance monitors that are applicable to the mashup application that is being created in a mashup application development environment, at a user device for selection; and instructing the mashup application development environment to embed selected ones of the mashup application performance monitors into the mashup application that is being created in the mashup application development environment, responsive to a selection of the selected ones of the mashup application performance monitors from the mashup application performance monitors that are applicable to the mashup application that is being created in the mashup application development environment, wherein the matching ones of the mashup application performance monitors that are applicable to the mashup application that is being created in the mashup application development environment comprise default mashup application performance monitors that are applicable to the mashup application that is being created in the mashup application development environment, and that are included in the selected ones of the mashup application performance monitors unless deselected.