Python: Skip MCP prompt loading when unsupported

[karimbaidar]

Motivation and Context

Fixes #5360.

MCP servers can advertise tools without supporting prompts. The client was still calling prompts/list whenever prompt loading was enabled, so tool-only servers could fail during connect.

Description

Stores the server capabilities returned by MCP initialization and skips prompt discovery when the server does not advertise the prompts capability. If capabilities are unavailable, the existing behavior is preserved.

Adds a focused core MCP regression test for a tool-only server that would otherwise raise Method 'prompts/list' is not available.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? No

[karimbaidar]

@microsoft-github-policy-service agree

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework
_mcp.py	625	32	94%	153, 295, 355–356, 485, 547, 560, 562–565, 584–585, 598–601, 603–604, 608, 672–674, 722–723, 1047, 1160, 1212–1213, 1216, 1234, 1687
TOTAL	28386	3300	88%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
5666	30 💤	0 ❌	0 🔥	1m 36s ⏱️

[Copilot]

Pull request overview

This PR fixes MCP client connections to tool-only servers by honoring negotiated server capabilities from MCP initialization, avoiding prompt discovery calls when the server does not support prompts.

Changes:

• Cache MCP initialize() capabilities on MCPTool and use them to detect prompt support.
• Skip prompts/list discovery when the server does not advertise the prompts capability (preserving existing behavior when capabilities are unavailable).
• Add a regression test ensuring prompt discovery is skipped for tool-only servers.

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	Store negotiated server capabilities and gate prompt loading on prompts capability support.
python/packages/core/tests/core/test_mcp.py	Add regression coverage for connecting to a server that supports tools but not prompts.