docs: clarify local file connector setup

contracts/service-v1.json

@@ -1049,7 +1049,7 @@
       "name": "source_capture_url"
     },
     {
-      "description": "Begin a bounded source upload scoped to an authorized project.",
+      "description": "Begin a low-level upload for a byte-capable client such as gewu-connector.\n\nFor files on the agent's machine, configure and use the local stdio\nconnector instead of sending source bytes through conversational calls.\n",
       "input_schema": {
         "properties": {
           "byte_length": {
@@ -1103,7 +1103,7 @@
       "name": "source_upload_status"
     },
     {
-      "description": "Transfer one integrity-checked upload chunk.",
+      "description": "Transfer one integrity-checked chunk for a byte-capable upload client.\n\nThis low-level endpoint is used internally by gewu-connector. Do not\nsend whole-file base64 through conversational MCP; configure the local\nconnector for files on the agent's machine.\n",
       "input_schema": {
         "properties": {
           "chunk_sha256": {
@@ -1135,7 +1135,7 @@
       "name": "source_upload_chunk"
     },
     {
-      "description": "Finalize and content-address a supported file or UTF-8 transcript artifact.",
+      "description": "Finalize a low-level upload after all verified chunks are present.\n\nLocal-file connector workflows handle upload and finalization internally.\n",
       "input_schema": {
         "properties": {
           "upload_id": {