# m4t.tf: Developers

> The machine-readable surface of Matt Fehrenbach's site. This guide scopes the
> retrieval interface for agents that read the site's resources.

## Resources

- [/.well-known/agent-skills/index.json](https://m4t.tf/.well-known/agent-skills/index.json): The Agent Skills the site publishes for agents.
- [/.well-known/ai-catalog.json](https://m4t.tf/.well-known/ai-catalog.json): The AI catalogue of the site's agent-facing resources.
- [/.well-known/api-catalog](https://m4t.tf/.well-known/api-catalog): A machine-readable catalogue of published resources.
- [/.well-known/ard.json](https://m4t.tf/.well-known/ard.json): The ARD manifest of the site's agent-facing resources.
- [/llms-full.txt](https://m4t.tf/llms-full.txt): The published-content archive for agent retrieval.
- [/llms.txt](https://m4t.tf/llms.txt): A guide to the site and when agents should use it.
- [/openapi.json](https://m4t.tf/openapi.json): This machine-readable resource catalogue.
- [/robots.txt](https://m4t.tf/robots.txt): Crawler instructions and the sitemap location.
- [/rss.xml](https://m4t.tf/rss.xml): The feed of published blog posts.
- [/schemamap.xml](https://m4t.tf/schemamap.xml): The schema.org structured-data feeds the site publishes for agents.
- [/server.json](https://m4t.tf/server.json): The registry manifest for the m4t.tf server.
- [/sitemap.xml](https://m4t.tf/sitemap.xml): The indexable site pages.

## Retrieval

Request any page with `Accept: text/markdown` to receive it as markdown, or append
`.md` to the path, for example `https://m4t.tf/about.md`. Send
`Accept: application/json` to a resource to receive its canonical document or a typed
descriptor. Responses carry `Vary: Accept, Accept-Encoding`.

## Errors

Nonexistent paths return a real HTTP 404. The error follows the same negotiation:
`Accept: application/json` returns an RFC 9457 `application/problem+json` document,
and `Accept: text/markdown` returns the error as markdown. The whole interface is
described by the OpenAPI 3.1 document at [openapi.json](https://m4t.tf/openapi.json).

## Versioning

Send `API-Version` to declare the compatibility version you expect; the current
version is 1 and is the default. Deprecated resources carry RFC 9745 `Deprecation`
and RFC 8594 `Sunset` headers.

## Rate Limits

Every page and resource is unmetered.
`POST /ask` and the `ask` tool on `POST /mcp` are metered at 20 requests
per minute per client, sharing one budget, and return `429 Too Many Requests`
with `Retry-After` past it. Metered responses carry `RateLimit`, `RateLimit-Policy`,
`RateLimit-Limit`, `RateLimit-Remaining`, and `RateLimit-Reset` headers.

## MCP

- [MCP server](https://m4t.tf/mcp): Streamable HTTP, pinned to revision `2026-07-28`.
- [MCP server card](https://m4t.tf/.well-known/mcp/server-card.json): the card listing the `ask` tool.