test: add functional test for getopenrpcinfo

diff --git a/test/functional/rpc_openrpc.py b/test/functional/rpc_openrpc.py
new file mode 100755
index 00000000..b5d24d80
--- /dev/null
+++ b/test/functional/rpc_openrpc.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+# Copyright (c) 2026 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Check that getopenrpcinfo RPC is callable and serializable as valid json."""
+
+import json
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+
+def find_method(openrpc, name):
+    return next(method for method in openrpc["methods"] if method["name"] == name)
+
+
+def find_param(method, name):
+    return next(param for param in method["params"] if param["name"] == name)
+
+
+class OpenRPCDocTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def run_test(self):
+        self.log.info("Calling getopenrpcinfo")
+        openrpc = self.nodes[0].getopenrpcinfo()
+        json.dumps(openrpc)
+        assert_equal(openrpc["openrpc"], "1.4.1")
+        assert_equal(type(openrpc["openrpc"]).__name__, "str")
+        assert_equal(type(openrpc["info"]).__name__, "dict")
+        assert_equal(type(openrpc["methods"]).__name__, "list")
+
+        stop = find_method(openrpc, "stop")
+        assert "wait" not in [param["name"] for param in stop["params"]]
+
+        self.log.info("Calling getopenrpcinfo with hidden commands")
+        openrpc_with_hidden = self.nodes[0].getopenrpcinfo(True)
+        stop_with_hidden = find_method(openrpc_with_hidden, "stop")
+        wait = find_param(stop_with_hidden, "wait")
+        assert_equal(wait["schema"]["type"], "number")
+
+        self.log.info("Checking type_str override schemas")
+        getblockstats = find_method(openrpc, "getblockstats")
+        hash_or_height = find_param(getblockstats, "hash_or_height")
+        assert_equal(hash_or_height["schema"], {"oneOf": [{"type": "number"}, {"type": "string"}]})
+
+        self.log.info("Checking fixed-length array schemas")
+        deriveaddresses = find_method(openrpc, "deriveaddresses")
+        range_array = find_param(deriveaddresses, "range")["schema"]["oneOf"][1]
+        assert_equal(range_array, {
+            "type": "array",
+            "items": [{"type": "number"}, {"type": "number"}],
+            "additionalItems": False,
+            "minItems": 2,
+            "maxItems": 2,
+        })
+
+        feerate_percentiles = getblockstats["result"]["schema"]["properties"]["feerate_percentiles"]
+        assert_equal(feerate_percentiles["type"], "array")
+        assert_equal(feerate_percentiles["items"], [{"type": "number"}] * 5)
+        assert_equal(feerate_percentiles["additionalItems"], False)
+        assert_equal(feerate_percentiles["minItems"], 5)
+        assert_equal(feerate_percentiles["maxItems"], 5)
+
+        self.log.info("Checking relaxed schemas for unchecked RPC types")
+        createrawtransaction = find_method(openrpc, "createrawtransaction")
+        outputs = find_param(createrawtransaction, "outputs")
+        assert_equal(outputs["schema"], {"oneOf": [{"type": "array"}, {"type": "object"}]})
+
+        getdescriptoractivity = find_method(openrpc, "getdescriptoractivity")
+        activity = getdescriptoractivity["result"]["schema"]["properties"]["activity"]
+        assert_equal(activity["type"], "array")
+
+        if "getwalletinfo" in [method["name"] for method in openrpc["methods"]]:
+            getwalletinfo = find_method(openrpc, "getwalletinfo")
+            scanning = getwalletinfo["result"]["schema"]["properties"]["scanning"]
+            assert_equal(scanning["oneOf"][0]["type"], "object")
+            assert_equal(scanning["oneOf"][1], {"const": False})
+
+        self.log.info("Checking argument fallback annotations")
+        getblock = find_method(openrpc, "getblock")
+        verbosity = find_param(getblock, "verbosity")
+        assert_equal(verbosity["schema"]["default"], 1)
+        stats = find_param(getblockstats, "stats")
+        assert_equal(stats["schema"]["x-bitcoin-default-hint"], "all values")
+
+        self.log.info("Checking string amount result annotations")
+        analyzepsbt = find_method(openrpc, "analyzepsbt")
+        result_schema = analyzepsbt["result"]["schema"]
+        estimated_feerate = result_schema["properties"]["estimated_feerate"]
+        assert_equal(estimated_feerate["type"], "string")
+        assert_equal(estimated_feerate["x-bitcoin-unit"], "amount")
+
+
+if __name__ == "__main__":
+    OpenRPCDocTest(__file__).main()
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 5bfc7d86..646d835c 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -393,6 +393,7 @@ BASE_SCRIPTS = [
     'wallet_migration.py',
     'p2p_ibd_txrelay.py',
     'p2p_seednode.py',
+    'rpc_openrpc.py',
     # Don't append tests at the end to avoid merge conflicts
     # Put them in a random line within the section that fits their approximate run-time
 ]