René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"MCP Server won't work with wildcard in \"Accept\" header and therefore is non‑compliant with HTTP spec","articleBody":"### Question\n\n### Use Case\nMy client sends a request to MCP Server with `Accept` header `*/*` (Same for `application/*, text/event-stream`). Server rejects this request because it expected strictly `application/json` or `application/json and text/event-stream` if  `json_response=False`.  \n\n### Expected\nAccording to the HTTP/1.1 spec (RFC 7231, section 5.3.2), the Accept header allows wildcard so values `*/*` and `application/*` should be valid, therefore server should accept them\n\n```\nfrom mcp.server.fastmcp import FastMCP\nfrom starlette.applications import Starlette\n\n...\n\nmcp_server: FastMCP = FastMCP(streamable_http_path=\"/\", stateless_http=True, json_response=True)\n\n...\n\napp: Starlette = mcp_server.streamable_http_app()\n```\nStart server: `uvicorn mcp-server:app --host 127.0.0.1 --port 8000 --log-level trace`\n\n### Example of Call\n```\n### Request\nPOST / HTTP/1.1.\nHost: localhost:8000.\nAccept-Encoding: gzip, deflate, br, zstd.\nConnection: keep-alive.\nUser-Agent: python-httpx/0.28.1.\nContent-Type: application/json.\nAccept: */*.\nContent-Length: 159.\n.\n\n{\"jsonrpc\":\"2.0\",\"id\":0,\"method\":\"initialize\",\"params\":{\"protocolVersion\":\"2025-06-18\",\"capabilities\":{},\"clientInfo\":{\"name\":\"mcp-client\",\"version\":\"1.0.0\"}}}\n\n\n### Response\nHTTP/1.1 406 Not Acceptable.\ndate: Tue, 18 Nov 2025 16:16:17 GMT.\nserver: uvicorn.\ncontent-type: application/json.\ncontent-length: 125.\n.\n\nT 127.0.0.1:8000 -\u003e 127.0.0.1:61346 [AP] #107\n{\"jsonrpc\":\"2.0\",\"id\":\"server-error\",\"error\":{\"code\":-32600,\"message\":\"Not Acceptable: Client must accept application/json\"}}\n```\n\n### Additional Context\n\n- mcp 1.18.0\n- Python 3.11.13\n- uvicorn 0.38.0\n- starlette 0.49.1","author":{"url":"https://github.com/rh-fr","@type":"Person","name":"rh-fr"},"datePublished":"2025-11-18T16:33:22.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/1641/python-sdk/issues/1641"}