Max
35 lines
1.2 KiB
Python
35 lines
1.2 KiB
Python
"""Two error channels: ToolError -> is_error result; MCPError -> JSON-RPC protocol error."""
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from mcp.server.mcpserver import MCPServer
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from mcp.server.mcpserver.exceptions import ToolError
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from mcp.shared.exceptions import MCPError
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from mcp.types import INVALID_PARAMS
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from stories._hosting import run_server_from_args
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def build_server() -> MCPServer:
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mcp = MCPServer("error-handling-example")
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@mcp.tool()
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def divide(a: float, b: float) -> float:
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"""Divide a by b. Division by zero is an execution error the LLM should see."""
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if b == 0:
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# ToolError is caught by the tool wrapper and returned as
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# CallToolResult(is_error=True) — the LLM reads the message and can
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# self-correct.
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raise ToolError("cannot divide by zero")
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return a / b
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@mcp.tool()
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def restricted() -> str:
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"""A tool that always rejects the caller at the protocol level."""
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# MCPError escapes the tool wrapper and becomes a JSON-RPC error
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# response — the *host* sees code/message/data, not the LLM.
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raise MCPError(code=INVALID_PARAMS, message="this tool is gated", data={"reason": "demo"})
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return mcp
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if __name__ == "__main__":
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run_server_from_args(build_server)
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