diff --git a/runtime/binding-mcp-openapi/src/main/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGenerator.java b/runtime/binding-mcp-openapi/src/main/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGenerator.java
index e930e223e8..61a8c88cf9 100644
--- a/runtime/binding-mcp-openapi/src/main/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGenerator.java
+++ b/runtime/binding-mcp-openapi/src/main/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGenerator.java
@@ -1117,6 +1117,7 @@ private static String inputSchema(
         final JsonObjectBuilder properties = Json.createObjectBuilder();
         final List<String> required = new LinkedList<>();
         final List<String> propertyNames = new LinkedList<>();
+        JsonValue additionalProperties = null;
 
         if (operation.parameters != null)
         {
@@ -1161,6 +1162,11 @@ private static String inputSchema(
                         }
                     }
                 }
+                if (schema != null && schema.model.additionalProperties != null &&
+                    !JsonValue.FALSE.equals(schema.model.additionalProperties))
+                {
+                    additionalProperties = schema.model.additionalProperties;
+                }
                 break;
             }
         }
@@ -1174,6 +1180,10 @@ private static String inputSchema(
             required.forEach(requiredArray::add);
             object.add("required", requiredArray);
         }
+        if (additionalProperties != null)
+        {
+            object.add("additionalProperties", additionalProperties);
+        }
 
         return object.build().toString();
     }
diff --git a/runtime/binding-mcp-openapi/src/test/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGeneratorTest.java b/runtime/binding-mcp-openapi/src/test/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGeneratorTest.java
index e6bb5026a9..9b0de35789 100644
--- a/runtime/binding-mcp-openapi/src/test/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGeneratorTest.java
+++ b/runtime/binding-mcp-openapi/src/test/java/io/aklivity/zilla/runtime/binding/mcp/openapi/internal/config/composite/McpOpenapiCompositeGeneratorTest.java
@@ -838,6 +838,86 @@ public void shouldDenyPathParameterInOpenBodySchema()
         assertThat(bodySchemaObject.getBoolean("additionalProperties"), equalTo(true));
     }
 
+    @Test
+    public void shouldAdvertiseAdditionalPropertiesInInputSchema()
+    {
+        String spec =
+            """
+            {
+              "openapi": "3.0.1",
+              "info": { "title": "things", "version": "1.0" },
+              "servers": [ { "url": "https://api.example.com" } ],
+              "paths": {
+                "/things/{id}": {
+                  "put": {
+                    "operationId": "update_thing",
+                    "parameters": [
+                      { "name": "id", "in": "path", "required": true, "schema": { "type": "string" } }
+                    ],
+                    "requestBody": {
+                      "required": true,
+                      "content": { "application/json": { "schema": {
+                        "type": "object",
+                        "properties": { "name": { "type": "string" } },
+                        "additionalProperties": true } } }
+                    },
+                    "responses": { "200": { "description": "ok" } }
+                  }
+                }
+              }
+            }
+            """;
+        lenient().when(catalog.resolve(eq("things-api"), eq("latest"))).thenReturn(77);
+        lenient().when(catalog.resolve(eq(77))).thenReturn(spec);
+
+        BindingConfig binding = GenericBindingConfig.builder()
+            .namespace("test")
+            .name("mcp-openapi0")
+            .type("mcp-openapi")
+            .kind(CLIENT)
+            .options(McpOpenapiOptionsConfig.builder()
+                .spec()
+                    .label("openapi_things0")
+                    .server("https://api.example.com")
+                    .catalog()
+                        .name("catalog0")
+                        .subject("things-api")
+                        .version("latest")
+                        .build()
+                    .build()
+                .build())
+            .route()
+                .when(McpOpenapiConditionConfig.builder()
+                    .tool("update_thing")
+                    .build())
+                .with(McpOpenapiWithConfig.builder()
+                    .spec("openapi_things0")
+                    .operation("update_thing")
+                    .build())
+                .build()
+            .build();
+        binding.resolveId = resolveId;
+
+        McpOpenapiCompositeConfig composite = generator.generate(new McpOpenapiBindingConfig(context, binding));
+
+        NamespaceConfig namespace = composite.namespaces.get(0);
+        String inputSchema = namespace.catalogs.stream()
+            .map(c -> c.options)
+            .filter(InlineOptionsConfig.class::isInstance)
+            .map(InlineOptionsConfig.class::cast)
+            .flatMap(o -> o.subjects.stream())
+            .filter(s -> "update_thing-input".equals(s.subject))
+            .map(s -> s.schema)
+            .findFirst()
+            .orElse(null);
+
+        assertThat(inputSchema, notNullValue());
+        JsonObject inputSchemaObject = Json.createReader(new StringReader(inputSchema)).readObject();
+        assertThat(inputSchemaObject.getJsonObject("properties").containsKey("id"), equalTo(true));
+        assertThat(inputSchemaObject.getJsonObject("properties").containsKey("name"), equalTo(true));
+        assertThat(inputSchemaObject.getBoolean("additionalProperties"), equalTo(true));
+    }
+
     @Test
     public void shouldOverrideOutputSchema()
     {
diff --git a/specs/binding-mcp-kafka-connect.spec/src/main/scripts/io/aklivity/zilla/specs/binding/mcp/kafka/connect/streams/mcp/tools.list/client.rpt b/specs/binding-mcp-kafka-connect.spec/src/main/scripts/io/aklivity/zilla/specs/binding/mcp/kafka/connect/streams/mcp/tools.list/client.rpt
index 3bc8dbc53a..1cf39a3198 100644
--- a/specs/binding-mcp-kafka-connect.spec/src/main/scripts/io/aklivity/zilla/specs/binding/mcp/kafka/connect/streams/mcp/tools.list/client.rpt
+++ b/specs/binding-mcp-kafka-connect.spec/src/main/scripts/io/aklivity/zilla/specs/binding/mcp/kafka/connect/streams/mcp/tools.list/client.rpt
@@ -56,8 +56,8 @@ read  '{"tools":[{"name":"list_connectors","title":"List Connectors","descriptio
         '{"name":"describe_connector","title":"Describe Connector","description":"Read the configuration and task list of a connector.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
         '{"name":"delete_connector","title":"Delete Connector","description":"Delete a connector.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":false,"destructiveHint":true,"idempotentHint":true,"openWorldHint":false}},'
         '{"name":"describe_connector_config","title":"Describe Connector Config","description":"Read the effective configuration of a connector.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"outputSchema":{"type":"object"},"annotations":{"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
-        '{"name":"update_connector_config","title":"Update Connector Config","description":"Create or update a connector by setting its full configuration.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"},"connector.class":{"type":"string"},"tasks.max":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":false,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
-        '{"name":"validate_connector_config","title":"Validate Connector Config","description":"Validate a connector configuration against a plugin configuration definition, without creating or updating any connector.","inputSchema":{"type":"object","properties":{"pluginName":{"type":"string"},"connector.class":{"type":"string"},"tasks.max":{"type":"string"}},"required":["pluginName"]},"annotations":{"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
+        '{"name":"update_connector_config","title":"Update Connector Config","description":"Create or update a connector by setting its full configuration.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"},"connector.class":{"type":"string"},"tasks.max":{"type":"string"}},"required":["connector"],"additionalProperties":true},"annotations":{"readOnlyHint":false,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
+        '{"name":"validate_connector_config","title":"Validate Connector Config","description":"Validate a connector configuration against a plugin configuration definition, without creating or updating any connector.","inputSchema":{"type":"object","properties":{"pluginName":{"type":"string"},"connector.class":{"type":"string"},"tasks.max":{"type":"string"}},"required":["pluginName"],"additionalProperties":true},"annotations":{"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
         '{"name":"describe_connector_status","title":"Describe Connector Status","description":"Read the current state of a connector and the state of each of its tasks.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'
         '{"name":"restart_connector","title":"Restart Connector","description":"Restart a connector.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":false,"destructiveHint":false,"idempotentHint":false,"openWorldHint":false}},'
         '{"name":"pause_connector","title":"Pause Connector","description":"Pause a connector and all of its tasks.","inputSchema":{"type":"object","properties":{"connector":{"type":"string"}},"required":["connector"]},"annotations":{"readOnlyHint":false,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}},'