Support mcp 2.x (Python SDK): pin blocks mcp 2.0.0

Summary

crewAI currently pins the MCP Python SDK to the 1.x line and therefore cannot be installed alongside mcp 2.0.0 (released 2026-07-28). This issue tracks the breaking changes in mcp 2.0 that affect crewAI and what it would take to support it.

Current pins

Both hard-cap the SDK below 2.0.

Breaking changes in mcp 2.0 that affect crewAI

Verified against the installed mcp==2.0.0 SDK and crewAI main:

1. streamablehttp_client renamed → streamable_http_client, and now yields a 2-tuple instead of a 3-tuple. It yields (read_stream, write_stream); the third get_session_id element is gone. Used in 3 places with the old name + 3-tuple unpack:

   • lib/crewai/src/crewai/mcp/transports/http.py:75,77,84 — read, write, _ = await self._transport_context.__aenter__()
   • lib/crewai/src/crewai/mcp/tool_resolver.py:601,605 — async with streamablehttp_client(server_url) as (read, write, _)
   • lib/crewai/src/crewai/tools/mcp_tool_wrapper.py:165,173,175 — as (read, write, _)

2. streamable_http_client dropped the headers kwarg. Its 2.0 signature is (url, *, http_client=None, terminate_on_close=True). Custom headers must now be set on an httpx2.AsyncClient passed as http_client= (e.g. via mcp.shared._httpx_utils.create_mcp_http_client(headers=...)). This affects transports/http.py:78-80, which passes headers=self.headers.

3. camelCase attribute reads on mcp.types → snake_case. Constructing with camelCase aliases still parses, but attribute access must now be snake_case:

   • client.py:418 — getattr(tool, "inputSchema", {}) → input_schema
   • client.py:598 — getattr(result, "isError", False) → is_error
   • tool_resolver.py:619,621 — tool.inputSchema → input_schema
   • lib/crewai-tools/src/crewai_tools/adapters/mcp_adapter.py:54 — mcp_tool.inputSchema → input_schema

4. Dependency-floor updates. mcp 2.0 requires pydantic>=2.12, anyio>=4.9, typing-extensions>=4.13, and adds required deps opentelemetry-api and mcp-types (exact-pinned to the SDK version); httpx/httpx-sse are replaced by httpx2>=2.5.0. The crewai-tools[mcp] path additionally depends on the third-party mcpadapt bridge, so that path's 2.0 support is gated on mcpadapt adding 2.0 compatibility too.

Notes

• crewAI uses only the raw mcp SDK — no fastmcp dependency — so it is not transitively blocked the way some frameworks are. The native client code is also nicely centralized under lib/crewai/src/crewai/mcp/, which keeps the migration surface small (~5 modules).
• Already compatible, no change needed: SessionMessage still exists in 2.0 (mcp/shared/message.py:59), so transports/base.py:8 is fine. crewAI does not use McpError, read_timeout_seconds=timedelta(...), the removed mcp.types.Content/Cursor/ResourceReference, or the removed lowlevel @server.list_tools()/@server.call_tool() decorators (crewAI is a pure MCP client).

Happy to help with a PR if the maintainers are open to it.

Start with the MCP client modules listed in lib/crewai/src/crewai/mcp/, especially transports/http.py, tool_resolver.py, and mcp_tool_wrapper.py, then review client.py and lib/crewai-tools/src/crewai_tools/adapters/mcp_adapter.py. Check the dependency declarations in both pyproject.toml files and verify behavior against mcp 2.0. Done means the client handles the renamed transport, tuple and attribute changes, dependency floors, and the mcpadapt compatibility constraint.