fix: correct MCPServer call_tool result type (#2816) #2827

Job	Run time
checks / readme-snippets	15s
checks / pre-commit	46s
checks / test (3.10, locked, windows-latest)	1m 38s
checks / test (3.10, lowest-direct, windows-latest)	1m 40s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.10, locked, ubuntu-latest)	1m 1s
checks / test (3.12, lowest-direct, windows-latest)	1m 27s
checks / test (3.12, locked, ubuntu-latest)	1m 6s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 6s
checks / test (3.11, lowest-direct, windows-latest)	1m 44s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.11, locked, windows-latest)	1m 25s
checks / test (3.13, locked, windows-latest)	1m 38s
checks / test (3.13, lowest-direct, windows-latest)	1m 30s
checks / test (3.13, locked, ubuntu-latest)	55s
checks / test (3.13, lowest-direct, ubuntu-latest)	59s
checks / test (3.14, locked, windows-latest)	2m 16s
checks / test (3.14, lowest-direct, windows-latest)	1m 25s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 0s
checks / test (3.11, locked, ubuntu-latest)	1m 0s
checks / test (3.14, locked, ubuntu-latest)	1m 58s
checks / test (3.12, locked, windows-latest)	1m 27s
all-green	2s
	28m 26s

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