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Overview

The Agent Filesystem Interface defines an abstract interface for exposing arbitrary data sources to AI agents as a POSIX-shaped filesystem.

Implementations of this interface are called AFI providers. Software that consumes providers is called an AFI client (typically an agent runtime).

AFI is transport-agnostic. The transports section specifies concrete bindings for MCP, HTTP, FUSE, and SSH. Any binding that preserves the semantics defined in this specification is conformant.

Structure

The spec is organized as follows:

  • Terminology defines the words this spec uses precisely.
  • Path model governs what a valid AFI path is and how paths are compared.
  • Basic covers cross-cutting concerns: discovery via the manifest, access control, structured errors, and the extension model.
  • Operations are the four core verbs (stat, list, read, search) — each has its own page with request and response schemas.
  • Schemas defines the two shared data types (Entry, Match).
  • Transports specifies how operations travel: MCP tool calls, HTTP endpoints, FUSE callbacks, or SSH-hosted bash.
  • Conformance defines four profiles and the test kit that validates them.

What's not in v0.1

  • Streaming subscriptions or watch semantics (planned for v0.2)
  • Cross-provider federation (planned for v0.3)
  • Content-addressed storage semantics (out of scope)
  • Structured (non-text) match result formats (out of scope; use attributes on Entry)
  • Mutation operations (write, mkdir, delete, move) — reserved for AEP-0002

Conventions

  • Key words MUST, MUST NOT, SHOULD, SHOULD NOT, MAY are interpreted per RFC 2119 when in all caps.
  • Schemas use TypeScript-style syntax for readability. JSON Schema equivalents will be published alongside every numbered release.
  • Time values use RFC 3339 unless otherwise noted.