{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "textDocument/signatureHelp",
  "params": {
    "textDocument": {
      "uri": "file:///a/file.ts"
    },
    "position": {
      "character": 4,
      "line": 9
    },
    "context": {
      "triggerKind": 2,
      "triggerCharacter": "(",
      "isRetrigger": false
    }
  }
}