diff --git a/backend/open_webui/utils/tools.py b/backend/open_webui/utils/tools.py
index 0f18d2b753..ebf744d7d7 100644
--- a/backend/open_webui/utils/tools.py
+++ b/backend/open_webui/utils/tools.py
@@ -1668,6 +1668,7 @@ async def execute_tool_server(
         path_params = {}
         query_params = {}
         body_params = {}
+        declared_param_names = set()
 
         # Merge path-level and operation-level parameters for execution.
         path_level_params = methods.get('parameters', [])
@@ -1688,6 +1689,7 @@ async def execute_tool_server(
             param_name = param.get('name')
             if not param_name:
                 continue
+            declared_param_names.add(param_name)
             param_in = param.get('in')
             if param_name in params:
                 if param_in == 'path':
@@ -1707,8 +1709,16 @@ async def execute_tool_server(
         if query_params:
             final_url = f'{final_url}?{urlencode(query_params)}'
 
-        if operation.get('requestBody', {}).get('content'):
-            if params:
+        request_body_content = operation.get('requestBody', {}).get('content')
+        if request_body_content and params:
+            json_schema = request_body_content.get('application/json', {}).get('schema')
+            resolved_body_schema = resolve_schema(json_schema, openapi.get('components', {}))
+            is_composed_schema = any(keyword in resolved_body_schema for keyword in ('allOf', 'anyOf', 'oneOf'))
+            body_properties = {} if is_composed_schema else (resolved_body_schema.get('properties') or {})
+            # Strict servers reject declared parameters in the body, unless the body schema declares them too.
+            if body_properties:
+                body_params = {k: v for k, v in params.items() if k in body_properties or k not in declared_param_names}
+            else:
                 body_params = params
 
         async with aiohttp.ClientSession(
diff --git a/src/lib/apis/index.ts b/src/lib/apis/index.ts
index a6ece21d55..e5060fa888 100644
--- a/src/lib/apis/index.ts
+++ b/src/lib/apis/index.ts
@@ -1,5 +1,5 @@
 import { WEBUI_BASE_URL } from '$lib/constants';
-import { convertOpenApiToToolPayload } from '$lib/utils';
+import { convertOpenApiToToolPayload, resolveSchema } from '$lib/utils';
 import { normalizeTags } from '$lib/utils/tags';
 import { getOpenAIModelsDirect } from './openai';
 
@@ -598,10 +598,12 @@ export const executeToolServer = async (
 		const pathParams: Record<string, any> = {};
 		const queryParams: Record<string, any> = {};
 		let bodyParams: any = {};
+		const declaredParamNames = new Set<string>();
 
 		for (const param of mergedParams.values()) {
 			const paramName = param?.name;
 			if (!paramName) continue;
+			declaredParamNames.add(paramName);
 			const paramIn = param?.in;
 			if (params.hasOwnProperty(paramName)) {
 				if (paramIn === 'path') {
@@ -631,7 +633,24 @@ export const executeToolServer = async (
 		if (operation.requestBody && operation.requestBody.content) {
 			const contentType = Object.keys(operation.requestBody.content)[0];
 			if (params !== undefined) {
-				bodyParams = params;
+				const jsonSchema = operation.requestBody.content['application/json']?.schema;
+				const resolvedBodySchema = resolveSchema(jsonSchema, serverData.openapi.components);
+				const isComposedSchema = ['allOf', 'anyOf', 'oneOf'].some(
+					(keyword) => keyword in resolvedBodySchema
+				);
+				const bodyProperties = isComposedSchema ? {} : (resolvedBodySchema.properties ?? {});
+				// Strict servers reject declared parameters in the body, unless the body schema declares them too.
+				if (Object.keys(bodyProperties).length > 0) {
+					bodyParams = Object.fromEntries(
+						Object.entries(params).filter(
+							([key]) =>
+								Object.prototype.hasOwnProperty.call(bodyProperties, key) ||
+								!declaredParamNames.has(key)
+						)
+					);
+				} else {
+					bodyParams = params;
+				}
 			} else {
 				// Optional: Fallback or explicit error if body is expected but not provided
 				throw new Error(`Request body expected for operation '${name}' but none found.`);
diff --git a/src/lib/utils/index.ts b/src/lib/utils/index.ts
index 96b243c01a..91b66f8524 100644
--- a/src/lib/utils/index.ts
+++ b/src/lib/utils/index.ts
@@ -1464,7 +1464,11 @@ export const getLineCount = (text) => {
 };
 
 // Helper function to recursively resolve OpenAPI schema into JSON schema format
-function resolveSchema(schemaRef, components, resolvedSchemas = new Set()) {
+export function resolveSchema(
+	schemaRef,
+	components,
+	resolvedSchemas = new Set()
+): Record<string, any> {
 	if (!schemaRef) return {};
 
 	if (schemaRef['$ref']) {