Python: fix(python): treat any MCP ping JSON-RPC error as unsupported, not just -32601

[Diego Casati (dcasati)]

Hi,

MCPTool._ensure_connected() used a periodic ping as a connection health check.

When the server rejected ping with an McpError, the code only treated error code -32601 ("Method not found", the JSON-RPC-spec-correct code for an unimplemented method) as "ping unsupported, keep using this connection". Any other error code fell through to a reconnect attempt.

It seems like some real-world MCP servers (like the Microsoft Fabric's Data Agent MCP endpoint) reject an unsupported ping with a different code (-32600 "Invalid Request") instead. Since that server only implements initialize, notifications/initialized, tools/list, and tools/call, every single tool call triggered this same failed-ping path, and instead of just disabling future pings, the client attempted an unnecessary reconnect. That reconnect can itself fail in ways unrelated to the original (harmless) ping rejection, breaking an otherwise fully working MCP tool.

Any well-formed JSON-RPC error response to ping - regardless of its specific error code - already proves the connection is alive: the server received the request and replied. It just means the server doesn't support (or accept) the optional ping method.

This change treats any McpError from send_ping() the same way: disable future pings and continue using the existing connection, without attempting a reconnect. Only non-McpError exceptions (timeouts, transport/connection failures) -- where we genuinely don't know if the server is still reachable -- still trigger a reconnect, unchanged from before.

Added a regression test (nonstandard error code -32600) alongside the existing -32601 test to cover this.

Motivation & Context

Description & Review Guide

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Related Issue

Fixes #

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
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[Copilot]

Pull request overview

Updates MCP connection health checks to treat any JSON-RPC ping error as evidence of a live connection.

Changes:

• Disables future pings after any McpError.
• Retains reconnect behavior for transport and other non-MCP failures.
• Adds regression coverage for error code -32600.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/packages/core/agent_framework/_mcp.py	Broadens unsupported-ping handling.
python/packages/core/tests/core/test_mcp.py	Tests nonstandard ping error handling.

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Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework
_mcp.py	1386	110	92%	254, 260, 369, 388, 609, 688–689, 803, 828, 879, 994, 997, 1007, 1011, 1058–1059, 1064, 1071–1072, 1079, 1084–1085, 1092–1093, 1097, 1102–1103, 1112, 1119–1120, 1138, 1151, 1175–1176, 1195–1198, 1200–1201, 1205, 1231, 1265–1267, 1269, 1323–1325, 1384–1385, 1668, 1709–1710, 1723, 1726, 1735–1736, 1741–1742, 1748, 1802–1803, 1823–1824, 1833–1834, 1839–1840, 1846, 1939, 1942, 1969, 2029–2031, 2036, 2040–2041, 2143, 2150, 2152, 2223, 2238–2239, 2246–2247, 2252–2253, 2258, 2262, 2277, 2339, 2522, 2524, 2546, 2548–2551, 2564–2565, 2609, 2671, 3110–3111, 3156, 3376–3377, 3395
TOTAL	45957	4253	90%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
9358	36 💤	0 ❌	0 🔥	2m 8s ⏱️