diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index fca3996..60242ec 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,5 +1,4 @@
-Want to contribute? Great! First, read this page (including the small print at
-the end).
+Want to contribute? Great!
 
 ### Before you contribute
 Before you start working on a larger contribution, you should get in touch with
@@ -15,3 +14,35 @@ bugs have been acknowledged or fixed.
 ### Code reviews
 All submissions, including submissions by project members, require review. We
 use GitHub pull requests for this purpose.
+
+### Test schemas
+All new test types should be accompanied by [JSON schema] files describing the
+test vector data structure. See the [`schemas/` directory][schema dir] for
+existing examples.
+
+Test vector files are [linted in CI][schema lint] against their schemas. You can
+run the lint locally after installing Go with `go run ./tools/vectorlint`.
+
+#### Schema best practices
+
+All new schema files should:
+
+* Describe common top-level properties matching pre-existing schemas/vectors
+  (e.g. `algorithm`, `header`, `notes`, `numberOfTests`, and `schema`).
+* Divide vector files into test groups.
+* Use `"additionalProperties": false` in each defined object to prevent
+  unspecified fields in vector data.
+* Use `"required": [...]` in each defined object to specify the expected
+  mandatory properties in vector data.
+* Within each test group, specify a `source`, referencing the common
+  [`common.json#/definitions/Source`][source schema] element.
+* Avoid deprecated schema fields (e.g. `generatorVersion`).
+* Avoid duplicating complex schema elements across many schema files (e.g.
+  public key definitions). Instead, create a separate schema file for the common
+  object and [reference it][schema ref] throughout other schema files.
+
+[JSON schema]: https://json-schema.org/
+[schema dir]: https://github.com/C2SP/wycheproof/tree/main/schemas
+[schema lint]: https://github.com/C2SP/wycheproof/blob/main/.github/workflows/vectorlint.yml
+[source schema]: https://github.com/C2SP/wycheproof/blob/main/schemas/common.json
+[schema ref]: https://json-schema.org/understanding-json-schema/structuring#dollarref