Use a simple overwrite instead of a merge for meta (#1296)

src/fastmcp/server/proxy.py

@@ -256,7 +256,7 @@ class ProxyTool(Tool, MirroredComponent):
             annotations=mcp_tool.annotations,
             output_schema=mcp_tool.outputSchema,
             meta=mcp_tool.meta,
-            tags=(mcp_tool.meta or {}).get("tags", []),
+            tags=(mcp_tool.meta or {}).get("_fastmcp", {}).get("tags", []),
             _mirrored=True,
         )
 
@@ -305,6 +305,7 @@ class ProxyResource(Resource, MirroredComponent):
         mcp_resource: mcp.types.Resource,
     ) -> ProxyResource:
         """Factory method to create a ProxyResource from a raw MCP resource schema."""
+
         return cls(
             client=client,
             uri=mcp_resource.uri,
@@ -312,7 +313,7 @@ class ProxyResource(Resource, MirroredComponent):
             description=mcp_resource.description,
             mime_type=mcp_resource.mimeType or "text/plain",
             meta=mcp_resource.meta,
-            tags=(mcp_resource.meta or {}).get("tags", []),
+            tags=(mcp_resource.meta or {}).get("_fastmcp", {}).get("tags", []),
             _mirrored=True,
         )
 
@@ -353,7 +354,7 @@ class ProxyTemplate(ResourceTemplate, MirroredComponent):
             mime_type=mcp_template.mimeType or "text/plain",
             parameters={},  # Remote templates don't have local parameters
             meta=mcp_template.meta,
-            tags=(mcp_template.meta or {}).get("tags", []),
+            tags=(mcp_template.meta or {}).get("_fastmcp", {}).get("tags", []),
             _mirrored=True,
         )
 
@@ -387,7 +388,7 @@ class ProxyTemplate(ResourceTemplate, MirroredComponent):
             description=self.description,
             mime_type=result[0].mimeType,
             meta=self.meta,
-            tags=(self.meta or {}).get("tags", []),
+            tags=(self.meta or {}).get("_fastmcp", {}).get("tags", []),
             _value=value,
         )
 
@@ -422,7 +423,7 @@ class ProxyPrompt(Prompt, MirroredComponent):
             description=mcp_prompt.description,
             arguments=arguments,
             meta=mcp_prompt.meta,
-            tags=(mcp_prompt.meta or {}).get("tags", []),
+            tags=(mcp_prompt.meta or {}).get("_fastmcp", {}).get("tags", []),
             _mirrored=True,
         )
 

src/fastmcp/utilities/components.py

@@ -16,12 +16,6 @@ class FastMCPMeta(TypedDict, total=False):
     tags: list[str]
 
 
-def _merge_meta(left: FastMCPMeta, right: FastMCPMeta) -> FastMCPMeta:
-    return FastMCPMeta(
-        tags=sorted(set(left.get("tags", [])) | set(right.get("tags", [])))
-    )
-
-
 def _convert_set_default_none(maybe_set: set[T] | Sequence[T] | None) -> set[T]:
     """Convert a sequence to a set, defaulting to an empty set if None."""
     if maybe_set is None:
@@ -90,8 +84,9 @@ class FastMCPComponent(FastMCPBaseModel):
 
         if include_fastmcp_meta:
             fastmcp_meta = FastMCPMeta(tags=sorted(self.tags))
+            # overwrite any existing _fastmcp meta with keys from the new one
             if upstream_meta := meta.get("_fastmcp"):
-                fastmcp_meta = _merge_meta(upstream_meta, fastmcp_meta)
+                fastmcp_meta = upstream_meta | fastmcp_meta
             meta["_fastmcp"] = fastmcp_meta
 
         return meta or None