--- title: Lookup definition description: Return fields and records for search and options inputs. --- Register a lookup with `resource.lookup(name, resolver)` or `resource.lookup(name, { params }, resolver)`. A name must be unique within its resource. The resolver receives `ctx` and a `LookupBuilder`. Read search text from `ctx.searchQuery` and parameters from `ctx.paramValues`. Return `lookup.setFields(fields).withData(rows)`. Use `setRoles(map)` to select field roles and `onDefect(reporter)` to handle invalid values. The default role is `display`. Extra record keys do not travel in the response. The SDK does not query your data store or filter records automatically. A search input sends the typed query. An options input sends an empty query. The host calls `app.handleLookup(resource, name, query, args)` for both. Use `lookupVia` or `optionsVia` to connect an input to the definition. Both check the selected `value` and `label` field names. Supply an argument for every parameter. Field arguments read the current form or repeater row. See [Lookup targets](/reference/targets/lookup). The definition exposes `resource`, `name`, and `params`. Its `resolve(ctx)` method returns a success response containing the lookup fields and data. Use the app method when middleware and address checks must run.