MCP prompt slash commands don't handle quoted multi-word arguments

Description

When invoking an MCP prompt via slash command with quoted multi-word arguments, the argument parser splits on whitespace and ignores quoting. Both double quotes ("...") and single quotes ('...') are affected.

Steps to Reproduce

1. MCP server exposes a prompt with 4 string parameters (artist, venue, date, tourName). Template:

Write a dramatic press release for {artist} performing '{tourName}' at {venue} on {date}.

1. Invoke via slash command:

``
/mcp__StarAgent__concert_press_release Queen "Metronom Theater Oberhausen" 26.06.2026 "The show must go on!"
``

1. Expected prompts/get call arguments:

• venue = Metronom Theater Oberhausen
• tourName = The show must go on!

1. Actual prompt received by Claude:

Write a dramatic press release for Queen performing 'Oberhausen"' at "Metronom on Theater.

Workaround

Using single-word arguments (no spaces) works correctly:

/mcp__StarAgent__concert_press_release Queen Metronom_Theater_Oberhausen 26.06.2026 TheShow

Environment

• Platform: macOS (Darwin 25.5.0)
• MCP transport: stdio