Tools (9)
Version
API and data versions.
API version follows [Semantic Versioning 2.0.0 Schema](https://semver.org/spec/v2.0.0.html).
Data version is UTC timestamp in `yyyy-MM-dd'T'HH:mm:ss` format.
List Field Sizes
Sizes of list/array fields.
To search studies by a list field size, use `AREA[FieldName:size]` search operator.
For example, [AREA\[Phase:size\] 2](https://clinicaltrials.gov/search?term=AREA%5BPhase:size%5D%202)
query finds studies with 2 phases.
Field Values
Value statistics of the study leaf fields.
Single Study
Returns data of a single study.
Studies
Returns data of studies matching query and filter parameters. The studies are returned page by page.
If response contains `nextPageToken`, use its value in `pageToken` to get next page.
The last page will not contain `nextPageToken`. A page may have empty `studies` array.
Request for each subsequent page **must** have the same parameters as for the first page, except
`countTotal`, `pageSize`, and `pageToken` parameters.
If neither queries nor filters are set, all studies will be returned.
If any query parameter contains only NCT IDs (comma- and/or space-separated), filters are ignored.
`query.*` parameters are in [Essie expression syntax](/find-studies/constructing-complex-search-queries).
Those parameters affect ranking of studies, if sorted by relevance. See `sort` parameter for details.
`filter.*` and `postFilter.*` parameters have same effect as there is no aggregation calculation.
Both are available just to simplify applying parameters from search request.
Both do not affect ranking of studies.
Note: When trying JSON format in your browser, do not set too large `pageSize` parameter, if `fields` is
unlimited. That may return too much data for the browser to parse and render.
Data Model Fields
Returns study data model fields.
Search Areas
Search Docs and their Search Areas.
Enums
Returns enumeration types and their values.
Every item of the returning array represents enum type and contains the following properties:
* `type` - enum type name
* `pieces` - array of names of all data pieces having the enum type
* `values` - all available values of the enum; every item contains the following properties:
* `value` - data value
* `legacyValue` - data value in legacy API
* `exceptions` - map from data piece name to legacy value when different from `legacyValue`
(some data pieces had special enum values in legacy API)
Study Sizes
Statistics of study JSON sizes.