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

> Recent development. Anthropic adopted the standard i created. their
> new agents format is a markdown file with YAML Frontmatter and it was

>From what I can tell, Anthropic did not adopt this format.  They happened to also use YAML front matter, which is a very common technique, with a name, description and tools property.
The anthropic file format https://docs.anthropic.com/en/docs/claude-code/sub-agents#file-format documentation provides no reference to the schema dot.agent/docs/schema.md at main · agentbrazley/dot.agent · GitHub<https://github.com/agentbrazley/dot.agent/blob/main/docs/schema.md> for the media type registration being proposed.

Anthropic only mentions three properties and the syntax of the tools property doesn't match.

If the request wishes to try and bring this proposed format to a standards body, then I would recommend posting on the IETF agent2agent mailing list to try and get support for this format https://mailman3.ietf.org/mailman3/lists/agent2agent.ietf.org/

Regards,

Darrel

________________________________
From: Amanda Baber via RT <[email protected]>
Sent: Friday, August 29, 2025 3:33 PM
Cc: [email protected] <[email protected]>; Darrel Miller <[email protected]>
Subject: [IANA #1421838] application/vnd.agent+markdown registration request

Hi Darrel,

Sending a reminder for this reconsideration request/update from July 29th.

thanks,
Amanda

On Tue Jul 29 00:11:40 2025, david.dong wrote:
> Hi Darrel (filling in for Amanda),
>
> The requester sent the follow-up statement:
>
> --
>
> Recent development. Anthropic adopted the standard i created. their
> new agents format is a markdown file with YAML Frontmatter and it was
> deployed globaly to all claude code users. Instead of using the .agent
> endpoint they just create the file within their own system but it is
> literally stored in the “agents” folder and uses the exact same
> system.
>
> Does that count as in use now?
>
> --
>
> Best regards,
>
> David Dong
> IANA Services Sr. Specialist
>
> On Mon Jul 21 20:13:16 2025, amanda.baber wrote:
> > Hi Darrel,
> >
> > We received thanks and a question from the requester: "Do you or the
> > reviewer know what standards body I would need to apply with instead?
> > I’ve never tried to do anything like this before and this is who I
> > was
> > recommended to apply with. Any help on who to apply with, or how to
> > change this so that it’s the right thing would be extremely helpful."
> >
> > thanks,
> > Amanda
> >
> > On Tue Jul 15 20:19:10 2025, [email protected] wrote:
> > > The field "Applications which use this media" is intended to
> > > describe
> > > applications that do use the media type, not ones that could use
> > > the
> > > media type.
> > >
> > > I think that a standardization effort around a declarative agent
> > > format would be excellent.  I would encourage you to explore that
> > > possibility through a recognized standards body and then it would
> > > be
> > > appropriate to register a media type in the standards tree as
> > > "application/agent+markdown.  The vendor subtree is not intended as
> > > a
> > > way to register something as a standard in the hope that it will
> > > become a standard.
> > >
> > > > The reason for using .agent is exactly because it is so broad.
> > > > That
> > > > way no company could lay claim to it.
> > >
> > > But that is what you are asking to do.  You are asking to connect
> > > the
> > > format that you designed, with a broadly applicable name.
> > > A broadly applicable standard should be designed via a
> > > collaboration
> > > with people in the space and the end result should be based on
> > > consensus.
> > >
> > > Regards,
> > >
> > > Darrel
> > > ________________________________
> > > From: Amanda Baber via RT <[email protected]>
> > > Sent: Tuesday, July 15, 2025 3:05 PM
> > > Cc: [email protected] <[email protected]>; Darrel Miller
> > > <[email protected]>
> > > Subject: [IANA #1421838] application/vnd.agent+markdown
> > > registration
> > > request
> > >
> > > Hi Darrel,
> > >
> > > Sending a reminder for this response from July 7th. (The time
> > > listed
> > > below is UTC.)
> > >
> > > thanks,
> > > Amanda
> > >
> > > On Tue Jul 08 00:40:03 2025, amanda.baber wrote:
> > > > Hi Darrel,
> > > >
> > > > The applicant sent the following response:
> > > >
> > > > =====
> > > >
> > > > I’m not saying it IS used by those. I’m saying it was written to
> > > > be
> > > > adopted by all of them using a format similar to what is already
> > > > present. Every one of those platforms has “instructions” for ai
> > > > but
> > > > with no standardization.. Claude Code uses CLAUDE.md. Gemini uses
> > > > GEMINI.md, etc.
> > > >
> > > > A product leader at Google tweeted about the need for
> > > > standardization
> > > > [text below]. That’s why I took it upon myself to write this. I
> > > > also
> > > > open sourced it on GitHub for that exact reason. I’m applying for
> > > > this
> > > > because people will need to be able to believe that it is a valid
> > > > format in order for it to be adopted, but It belongs to everyone
> > > > in
> > > > my
> > > > eyes. I just took what the product leader from google
> > > > (https://www.linkedin.com/in/kathleensimpson/) asked for a
> > > > delivered
> > > > a
> > > > uniform format.
> > > >
> > > > The reason for using .agent is exactly because it is so broad.
> > > > That
> > > > way no company could lay claim to it. If it was too specific I
> > > > feared
> > > > that one entity may try to lay claim to it. If approved, this
> > > > would
> > > > standardize something everyone using ai tools (especially
> > > > software
> > > > developers using CLI tools) use daily.
> > > >
> > > > Tweet from google product manager:
> > > > Hey @_catwu @AnthropicAI @OpenAI — can we standardize around
> > > > https://t.co/TXT5lybNcJ? There’s too much fragmentation right
> > > > now.
> > > > We
> > > > need a shared spec for agent definitions before this gets
> > > > messier.
> > > > Kath Korevec (@simpsoka)
> > > > x.com
> > > >
> > > > Response from me:
> > > > @simpsoka @_catwu @AnthropicAI @OpenAI Hey @simpsoka, @_catwu,
> > > > @AnthropicAI, & @OpenAI ... i created the ".agent" file type to
> > > > standardize this for everyone. Me and an agent just wrote it.
> > > > It's
> > > > basically markdown with mods so that everything will support it.
> > > > already. Hope you like it! I've already got it running. The
> > > > Quikokas (@Quikolas17)
> > > > x.com
> > > >
> > > > =====
> > > >
> > > > thanks,
> > > > Amanda
> > > >
> > > > On Sun Jul 06 22:31:44 2025, [email protected] wrote:
> > > > > 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]
> > > > > <media-
> > > > > [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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