Files
modelcontextprotocol--pytho…/docs_src/uri_templates/tutorial002.py
Max Isbey 4e0fc9ebcb Wrap crashing validators, treat ResourceError in a tool as anticipated
A custom argument validator that raises something other than
ValidationError escaped Tool.run unwrapped, losing the "Error executing
tool" prefix and the UnexpectedToolError type. It is now wrapped as a
crash, and an MCPError raised there still passes through.

A ResourceError (usually ResourceNotFoundError from ctx.read_resource)
that escapes a tool body is now classified like a ToolError, since it is
the same anticipated outcome resources/read logs at INFO. An
UnexpectedResourceError escaping a tool stays a crash.

MCPServer.read_resource is now the single place a resource crash is
wrapped (plus create_resource for templates), so the built-in Resource
types let the original exception propagate to direct callers.

Also: trimmed raise-site comments in favour of the exception docstrings,
reworded the ToolError and ResourceError docstrings, documented the
FunctionResource/FileResource.read change in migration.md, corrected the
uri-templates tip and example, and pinned the new cases in tests
(including a wire test for ResourceNotFoundError from a static resource).
2026-08-20 14:56:47 +00:00

19 lines
540 B
Python

from pathlib import Path
from mcp.server import MCPServer
from mcp.server.mcpserver.exceptions import ResourceNotFoundError
from mcp.shared.path_security import safe_join
mcp = MCPServer("Bookshop")
DOCS_ROOT = Path("./manuals")
@mcp.resource("manuals://{+path}")
def read_manual(path: str) -> str:
"""A staff manual page, served from a directory on disk."""
file = safe_join(DOCS_ROOT, path)
if not file.is_file():
raise ResourceNotFoundError(f"No manual at {path!r}.")
return file.read_text(encoding="utf-8")