Claude frequently passes a JSON string when setting frontmatter

[orf]

I'm not sure why, but Claude seems to frequently pass a string to the frontmatter argument when writing a note, even when instructed very specifically not to. this results in a large array of frontmatter values with each individual character.

⏺ obsidian - write_note (MCP)(path: "sessions/2026/03/05/foo.md", content: "bar", frontmatter: "{\"date\": \"2026-03-05\", \"type\": \"session\",  \"session_id\": \"e3a69763-12b5-41ac-8df0-2bf5b011cdf6\",
    \"tags\": [\"session\", \"feature\", \"error-handling\"]}")
  ⎿  Successfully wrote note: sessions/2026/03/05/foo.md (mode: overwrite)

    2 -'0': '{'
        3 -'1': '"'
        4 -'2': d
        5 -'3': a
        6 -'4': t
        7 -'5': e
        8 -'6': '"'
        9 -'7': ':'
       10 -'8': ' '
       11 -'9': '"'
       12 -'10': '2'
       13 -'11': '0'
       14 -'12': '2'
       15 -'13': '6'
       16 -'14': '-'
       17 -'15': '0'
       18 -'16': '3'
       19 -'17': '-'
       20 -'18': '0'
       21 -'19': '5'
       22 -'20': '"'
       23 -'21': ','
       24 -'22': ' '
       25 -'23': '"'

We could detect if a string is passed in, and attempt to deserialize it as JSON, and use that?

Claude says this:

⏺ I'm not sure what I'm doing differently from the expected format — could you
  clarify what you're seeing? In my tool call the frontmatter parameter value is
  unquoted JSON ({"date":"2026-03-05", ...}) between the XML tags, same as the merge
   parameter is unquoted false. Is there something else I need to change?

[bitbonsai]

Thanks again for the detailed report and examples. I have a candidate fix in PR #47 that parses string frontmatter values as JSON objects, but it needs a rebase and fresh CI before I merge it. I am keeping this issue open until that lands.

[orf]

Thanks @bitbonsai - i've rebased the PR 👍