kaxil opened a new pull request, #69006:
URL: https://github.com/apache/airflow/pull/69006
pydantic-ai deprecated `MCPServerStdio`, `MCPServerSSE`, and
`MCPServerStreamableHTTP` in favor of a unified `MCPToolset`, and removes all
three in pydantic-ai v2. The common.ai `MCPHook` constructed all three
directly, so it emits `DeprecationWarning`s today and would break on the v2
upgrade.
This migrates `MCPHook.get_conn()` to build an `MCPToolset` over the
matching FastMCP transport.
## What changed
| Transport | Before | After |
|---|---|---|
| `http` | `MCPServerStreamableHTTP(host, headers=…, tool_prefix=…)` |
`MCPToolset(StreamableHttpTransport(host, headers=…))` |
| `sse` | `MCPServerSSE(host, headers=…, tool_prefix=…)` |
`MCPToolset(SSETransport(host, headers=…))` |
| `stdio` | `MCPServerStdio(cmd, args=…, timeout=…, tool_prefix=…)` |
`MCPToolset(StdioTransport(command=cmd, args=…), init_timeout=…)` |
| prefix | `tool_prefix=` constructor arg | `.prefixed(prefix)` |
## Design rationale
- **Explicit transports instead of URL inference.** `MCPToolset` can infer a
transport from a bare URL, but FastMCP only picks SSE when the URL ends in
`/sse`. The connection has an explicit `transport` field, so the hook builds
the transport explicitly to honor that choice regardless of URL shape, and to
keep attaching the `Authorization` header.
- **`StdioTransport` for stdio.** The connection supplies an arbitrary
`command` + `args`, which is the case pydantic-ai's deprecation message
prescribes `StdioTransport(...)` for; the `MCPToolset("script.py")` shorthand
only covers literal script paths.
- **`.prefixed()` for `tool_prefix`.** `MCPToolset` has no `tool_prefix`
argument. `.prefixed(prefix)` produces the same `<prefix>_<tool>` names as
before and matches pydantic-ai's own `load_mcp_toolsets`. It returns a
`PrefixedToolset` that proxies the async-context-manager protocol, so the
connection-backed `MCPToolset` wrapper keeps working unchanged.
- **`init_timeout` is the successor to the old stdio `timeout`;** the hook
keeps its default of 10s.
## Tradeoffs / notes
- Behavior-preserving: tool names, auth headers, caching defaults, and the
no-auth path are unchanged.
- `fastmcp.client.transports` is the canonical public import path.
`pydantic_ai.mcp` imports from it, and pydantic-ai's own deprecation message
recommends `MCPToolset(fastmcp.client.transports.StdioTransport(...))`.
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