fix: improve MCP tool prompt clarity to prevent format confusion

[roomote]

Description

This PR addresses Issue #8507 where AI models were forgetting to use the use_mcp_tool wrapper when calling MCP tools, instead trying to call them directly by their tool name.

Problem

Users reported that when using MCP tools (like GitHub MCP), the AI would output incorrect format:

<get_pull_request>
  <owner>username</owner>
  <repo>repository</repo>
  <pullNumber>123</pullNumber>
</get_pull_request>

Instead of the correct format:

<use_mcp_tool>
  <server_name>github</server_name>
  <tool_name>get_pull_request</tool_name>
  <arguments>{...}</arguments>
</use_mcp_tool>

Solution

Enhanced the MCP tool prompts with:

• Explicit warnings about NOT using direct tool name format
• Clear examples showing incorrect (❌) vs correct (✅) usage
• Strong emphasis on the requirement to always use use_mcp_tool wrapper
• Reinforcement in both the tool description and MCP servers section

Changes

• Updated src/core/prompts/tools/use-mcp-tool.ts to include clear format instructions
• Updated src/core/prompts/sections/mcp-servers.ts to reinforce proper usage

Testing

• ✅ All existing tests pass
• ✅ Linting checks pass
• ✅ Type checking passes

Related Issues

Fixes #8507

Review Confidence

Implementation review showed 95% confidence with PROCEED recommendation.

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Important

Improves MCP tool prompt clarity in use_mcp_tool.ts and mcp-servers.ts to prevent format confusion by emphasizing correct usage with explicit warnings and examples.

• Behavior:
  • Updated use_mcp_tool.ts to emphasize correct usage of use_mcp_tool wrapper with explicit warnings and examples.
  • Updated mcp-servers.ts to reinforce the requirement to use use_mcp_tool wrapper and provide clear examples of correct vs incorrect formats.
• Testing:
  • All existing tests, linting, and type checks pass.

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[roomote]

Self-review: auditing my own prompt text like a mirror that files tickets.

[roomote]

P2: The inline example uses backslashes before closing XML tags (e.g., </server_name>). Within code spans, the backslash will be literal and may lead models to emit a backslash in their tool calls. Remove the backslashes so the example shows proper tags: </server_name>, </tool_name>, , </use_mcp_tool>. This also aligns with the examples in use-mcp-tool.ts.