Rename `FastMCP` to `MCPServer` by Kludex · Pull Request #1951 · modelcontextprotocol/python-sdk

Kludex · 2026-01-24T13:55:39Z

No description provided.

maxisbey · 2026-01-24T14:17:13Z

docs/migration.md

+from mcp.server.mcpserver import MCPServer

 # Transport params in constructor
-mcp = FastMCP("Demo", json_response=True, stateless_http=True)
+mcp = MCPServer("Demo", json_response=True, stateless_http=True)
 mcp.run(transport="streamable-http")

 # Or for SSE
-mcp = FastMCP("Server", host="0.0.0.0", port=9000, sse_path="/events")
+mcp = MCPServer("Server", host="0.0.0.0", port=9000, sse_path="/events")


Suggested change

from mcp.server.mcpserver import MCPServer

# Transport params in constructor

mcp = FastMCP("Demo", json_response=True, stateless_http=True)

mcp = MCPServer("Demo", json_response=True, stateless_http=True)

mcp.run(transport="streamable-http")

# Or for SSE

mcp = FastMCP("Server", host="0.0.0.0", port=9000, sse_path="/events")

mcp = MCPServer("Server", host="0.0.0.0", port=9000, sse_path="/events")

from mcp.server.fastmcp import FastMCP

# Transport params in constructor

mcp = FastMCP("Demo", json_response=True, stateless_http=True)

mcp.run(transport="streamable-http")

# Or for SSE

mcp = FastMCP("Server", host="0.0.0.0", port=9000, sse_path="/events")

maxisbey · 2026-01-24T14:18:35Z

src/mcp/server/fastmcp/__init__.py

@@ -1,8 +0,0 @@
-"""FastMCP - A more ergonomic interface for MCP servers."""


Guessing we don't want a backwards compatible shim since we'll be making breaking changes anyway?

maxisbey · 2026-01-24T14:25:02Z

docs/migration.md

 ```python
 # Before (v1)
-mcp = FastMCP("App", json_response=True)
+mcp = MCPServer("App", json_response=True)


Suggested change

mcp = MCPServer("App", json_response=True)

mcp = FastMCP("App", json_response=True)

maxisbey · 2026-01-24T14:25:38Z

docs/migration.md

 ```

-### `mount_path` parameter removed from FastMCP
+### `mount_path` parameter removed from MCPServer


add a section for the rename

maxisbey · 2026-01-24T14:28:07Z

src/mcp/server/mcpserver/utilities/func_metadata.py

    """Convert a result to a sequence of content objects.

-    Note: This conversion logic comes from previous versions of FastMCP and is being
+    Note: This conversion logic comes from previous versions of MCPServer and is being


Suggested change

Note: This conversion logic comes from previous versions of MCPServer and is being

Note: This conversion logic comes from previous versions of MCPServer (previously called FastMCP) and is being

very minor nit, probably easy to dismiss since we should remove this anyway

maxisbey · 2026-01-24T14:29:27Z

README.md

 ### Server

-The FastMCP server is your core interface to the MCP protocol. It handles connection management, protocol compliance, and message routing:
+The MCPServer server is your core interface to the MCP protocol. It handles connection management, protocol compliance, and message routing:


"The MCPServer Server" is gonna get confusing.. didn't think about that before

maxisbey · 2026-01-24T14:31:07Z

tests/server/mcpserver/test_server.py

-        mcp = FastMCP(
-            title="FastMCP Server",
+        mcp = MCPServer(
+            title="MCPServer Server",


"MCPServer Server" not super nice :/

maxisbey · 2026-01-24T14:32:12Z

src/mcp/server/mcpserver/server.py


    model_config = SettingsConfigDict(
-        env_prefix="FASTMCP_",
+        env_prefix="MCP_",


worth calling this out in migration docs

I think I'll drop this Settings before the end of the refactor.

maxisbey · 2026-01-24T14:34:14Z

tests/client/transports/test_memory.py

-    """Create a FastMCP server for testing."""
-    server = FastMCP("test")
+def mcpserver_server() -> MCPServer:
+    """Create a MCPServer server for testing."""


Suggested change

"""Create a MCPServer server for testing."""

"""Create an MCPServer server for testing."""

Should be "an" because MCPServer starts with an "em" sound.

maxisbey · 2026-01-24T14:39:05Z

tests/client/test_client.py

-    """Create a FastMCP server for testing."""
-    server = FastMCP("test")
+def app() -> MCPServer:
+    """Create a MCPServer server for testing."""


Suggested change

"""Create a MCPServer server for testing."""

"""Create an MCPServer server for testing."""

claude · 2026-01-24T20:42:08Z

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

claude · 2026-01-24T20:43:05Z

Code review

Issues Found

Missing PR Description (CLAUDE.md violation)

The PR body is empty, which violates the CLAUDE.md requirement for pull requests:

Create a detailed message of what changed. Focus on the high level description of the problem it tries to solve, and how it is solved. Don't go into the specifics of the code unless it adds clarity.

This PR performs a significant breaking change (renaming FastMCP to MCPServer across 123 files). The PR description should explain:

What problem the old naming caused or what improvement this provides
Why MCPServer is a better name than FastMCP
How this aligns with the project's direction and naming conventions

While the migration guide in docs/migration.md documents the technical changes, the PR description should provide the high-level rationale for reviewers and future reference.

Code Review Summary:

✅ No bugs found
✅ Breaking changes properly documented in docs/migration.md
✅ All imports, class references, and tests updated consistently
⚠️ PR description missing (CLAUDE.md violation)

Kludex · 2026-01-24T22:47:56Z

Rude.

Rename FastMCP to MCPServer

49b0ca4

maxisbey requested changes Jan 24, 2026

View reviewed changes

Kludex added 2 commits January 24, 2026 21:34

update migration

ab4f998

add an

dcca179

Kludex requested a review from maxisbey January 24, 2026 20:36

maxisbey approved these changes Jan 25, 2026

View reviewed changes

Kludex merged commit 65c614e into main Jan 25, 2026
30 checks passed

Kludex deleted the rename-fastmcp-to-mcpserver branch January 25, 2026 13:45

		@@ -1,8 +0,0 @@
		"""FastMCP - A more ergonomic interface for MCP servers."""

	mcp = MCPServer("App", json_response=True)
	mcp = FastMCP("App", json_response=True)

	Note: This conversion logic comes from previous versions of MCPServer and is being
	Note: This conversion logic comes from previous versions of MCPServer (previously called FastMCP) and is being

	"""Create a MCPServer server for testing."""
	"""Create an MCPServer server for testing."""

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Kludex commented Jan 24, 2026

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claude bot commented Jan 24, 2026

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claude bot commented Jan 24, 2026

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Kludex commented Jan 24, 2026

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