fix: include empty properties in get_me schema for OpenAI compatibility

OpenAI strict mode requires the `properties` field to be present in
object schemas, even when empty. The jsonschema library uses omitempty
which causes empty maps to be omitted during JSON serialization.

This change uses json.RawMessage to bypass the library's serialization
and explicitly include `"properties": {}` in the output.

Fixes #1548

Author: SamMorrowDrums

pkg/github/__toolsnaps__/get_me.snap

@@ -5,7 +5,8 @@
   },
   "description": "Get details of the authenticated GitHub user. Use this when a request is about the user's own profile for GitHub. Or when information is missing to build other tool calls.",
   "inputSchema": {
-    "type": "object"
+    "type": "object",
+    "properties": {}
   },
   "name": "get_me"
 }

pkg/github/context_tools.go

@@ -2,6 +2,7 @@ package github
 
 import (
 	"context"
+	"encoding/json"
 	"time"
 
 	ghErrors "github.com/github/github-mcp-server/pkg/errors"
@@ -43,9 +44,9 @@ func GetMe(getClient GetClientFn, t translations.TranslationHelperFunc) (mcp.Too
 				Title:        t("TOOL_GET_ME_USER_TITLE", "Get my user profile"),
 				ReadOnlyHint: true,
 			},
-			InputSchema: &jsonschema.Schema{
-				Type: "object",
-			},
+			// Use json.RawMessage to ensure "properties" is included even when empty.
+			// OpenAI strict mode requires the properties field to be present.
+			InputSchema: json.RawMessage(`{"type":"object","properties":{}}`),
 		},
 		mcp.ToolHandlerFor[map[string]any, any](func(ctx context.Context, _ *mcp.CallToolRequest, _ map[string]any) (*mcp.CallToolResult, any, error) {
 			client, err := getClient(ctx)