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Implement MCP server instructions handling: append instructions to system prompt in chat payload and add configuration option in AddToolServerModal.

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This commit is contained in:
Jacob Leksan 2026-04-06 14:31:17 -04:00
parent c40ea7f29d
commit 3064a73f16
3 changed files with 46 additions and 3 deletions
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9
backend/open_webui/utils/mcp/client.py
View file

@ -52,6 +52,8 @@ class MCPClient:
def __init__(self):
self.session: Optional[ClientSession] = None
self.exit_stack = None
# From InitializeResult.instructions (MCP protocol); forwarded to the model when using this server.
self.server_instructions: Optional[str] = None
async def connect(self, url: str, headers: Optional[dict] = None):
async with AsyncExitStack() as exit_stack:
@ -71,7 +73,11 @@ class MCPClient:
self.session = await exit_stack.enter_async_context(self._session_context)
with anyio.fail_after(10):
await self.session.initialize()
init_result = await self.session.initialize()
instr = getattr(init_result, 'instructions', None)
if isinstance(instr, str):
instr = instr.strip()
self.server_instructions = instr or None
self.exit_stack = exit_stack.pop_all()
except Exception as e:
await asyncio.shield(self.disconnect())
@ -153,6 +159,7 @@ class MCPClient:
# Prevent double-close from concurrent callers
self.exit_stack = None
self.session = None
self.server_instructions = None
try:
await asyncio.wait_for(

9
backend/open_webui/utils/middleware.py
View file

@ -2546,6 +2546,15 @@ async def process_chat_payload(request, form_data, user, metadata, model):
headers=headers if headers else None,
)
if mcp_server_connection.get('config', {}).get('forward_mcp_instructions', True):
mcp_instr = mcp_clients[server_id].server_instructions
if mcp_instr:
form_data['messages'] = add_or_update_system_message(
mcp_instr,
form_data['messages'],
append=True,
)
function_name_filter_list = mcp_server_connection.get('config', {}).get(
'function_name_filter_list', ''
)

31
src/lib/components/AddToolServerModal.svelte
View file

@ -50,6 +50,8 @@
let headers = '';
let functionNameFilterList = '';
/** MCP: append InitializeResult.instructions to the system prompt (backend). */
let forwardMcpInstructions = true;
let accessGrants = [];
let id = '';
@ -223,6 +225,9 @@
if (data.config) {
enable = data.config.enable ?? true;
accessGrants = data.config.access_grants ?? [];
if (data.config.forward_mcp_instructions !== undefined) {
forwardMcpInstructions = data.config.forward_mcp_instructions;
}
}
toast.success($i18n.t('Import successful'));
@ -252,7 +257,10 @@
id: id,
name: name,
description: description
}
},
...(type === 'mcp'
? { config: { forward_mcp_instructions: forwardMcpInstructions } }
: {})
}
]);
@ -329,7 +337,8 @@
config: {
enable: enable,
function_name_filter_list: functionNameFilterList,
access_grants: accessGrants
access_grants: accessGrants,
...(type === 'mcp' ? { forward_mcp_instructions: forwardMcpInstructions } : {})
},
info: {
id: id,
@ -368,6 +377,7 @@
enable = true;
functionNameFilterList = '';
forwardMcpInstructions = true;
accessGrants = [];
};
@ -394,6 +404,7 @@
enable = connection.config?.enable ?? true;
functionNameFilterList = connection.config?.function_name_filter_list ?? '';
forwardMcpInstructions = connection.config?.forward_mcp_instructions ?? true;
accessGrants = connection.config?.access_grants ?? [];
}
};
@ -880,6 +891,22 @@
</div>
</div>
{/if}
{#if type === 'mcp'}
<Tooltip
className="flex w-full items-center justify-between gap-3 mt-2"
content={$i18n.t(
'When enabled, instructions returned in the MCP initialize response are appended to the system prompt for chats that use this server.'
)}
>
<span
class={`text-xs font-medium ${($settings?.highContrastMode ?? false) ? 'text-gray-800 dark:text-gray-100' : 'text-gray-700 dark:text-gray-200'}`}
>
{$i18n.t('Include MCP server instructions')}
</span>
<Switch bind:state={forwardMcpInstructions} />
</Tooltip>
{/if}
{/if}
{#if !direct}