[media-types] Re: [IANA #1421838] application/vnd.ag ent+markdown registration request

Minor nit: The subtype name should just be vnd.agent+markdown

The bigger concern with this registration is that the term "agent" is very broadly applicable and this format is not broadly adopted from what I can tell. The registration claims that this format is used by Claude Code, Windsurf, VS Code, XCode, however, I can find no evidence of such support.  If the requester can provide such evidence, it would make the registration more appropriate.

Creating a registration for something like application/vnd.lancio.agent+markdown or application/vnd.agentbrazley.agent+markdown would be a reasonable alternative to what has been proposed.

Regards,

Darrel

________________________________
From: Amanda Baber via RT <[email protected]>
Sent: Monday, June 23, 2025 3:01 PM
Cc: Darrel Miller <[email protected]>; [email protected] <[email protected]>
Subject: [IANA #1421838] application/vnd.agent+markdown registration request

Hi Darrel,

New request here. Could you review this one for us by July 7th?

thanks,
Amanda

====

Name: Nikolas A. Brazley

Email: [email protected]

Media type name: application

Media subtype name: vnd. application/vnd.agent+markdown

Required parameters: N/A

Optional parameters: charset (default: UTF-8)
version (agent schema version, e.g., "1.0")

Encoding considerations: 8bit

8-bit text. Always UTF-8 encoded. Files are Markdown documents with
YAML frontmatter delimited by --- markers. The frontmatter section
must be valid YAML. The content section is standard Markdown.

Security considerations: .agent files are Markdown documents with YAML frontmatter that may contain references to external resources. Parsers should validate the YAML frontmatter against the published schema and sanitize inputs. Files may contain URLs or file paths that should be validated before processing. The Markdown content follows standard Markdown security considerations. No executable code is permitted in the format.

Interoperability considerations: Files must conform to YAML 1.2 specification with Jekyll-style frontmatter. The frontmatter section must be valid YAML between --- delimiters. Parsers should gracefully handle missing optional fields.

Published specification: https://github.com/agentbrazley/dot.agent
Full schema documentation at: https://github.com/nikbrazley/dot.agent/blob/main/docs/schema.md

Applications which use this media: - Claude Code
- IDE's with agentic capabilities (Cursor, Windsurf, VS Code, XCode, etc.)

Fragment identifier considerations: Fragment identifiers follow YAML/JSON Pointer syntax (RFC 6901) to reference specific fields within the frontmatter section.
Example: #/capabilities/0 references the first capability.

Restrictions on usage: none

Provisional registration? (standards tree only): No

Additional information:

1. Deprecated alias names for this type: N/A
2. Magic number(s): ---\n (0x2D2D2D0A in hex)
3. File extension(s): agent
4. Macintosh file type code:
5. Object Identifiers:

General Comments: The .agent file format consists of YAML frontmatter (delimited by ---) followed by optional Markdown content. The frontmatter contains structured metadata about AI agents following the schema documented at https://github.com/agentbrazley/dot.agent/blob/main/docs/schema.md

Files always begin with "---\n" and use UTF-8 encoding. The format is human-readable
and designed for version control systems.

Reference implementation: https://github.com/nikbrazley/dot.agent
npm package: agent-frontmatter

Person to contact for further information:

1. Name: Nik Brazley
2. Email: [email protected]

Intended usage: COMMON

Author/Change controller: Nik Brazley

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