attesto_mcp_server

attesto_mcp_server is an Apache-2.0, Attesto-native MCP server for Elixir. It provides one protocol core with MCP 2026-07-28 (preferred) and 2025-11-25 compatibility, a protected Plug-compatible Streamable HTTP boundary, and a line-oriented stdio adapter.

Protected HTTP traffic enters the approved AttestoMCP.Plug.ProtectResource boundary before body decoding and protocol dispatch, with route-derived scopes applied through its prepared dynamic authorization API. The required attesto_mcp ~> 1.2 dependency provides ProtectResource.prepare/1, authenticate/2, and authorize/3; no older authentication fallback is included. Configure the canonical resource path/origin, Attesto verifier, replay and certificate callbacks, and least-privilege scopes in the host application. The package does not contain an OAuth authorization server or token issuer.

Quick start

{:ok, server} = AttestoMCP.Server.start_link(name: :demo)

:ok = AttestoMCP.Server.register_tool(server, "hello", %{
  description: "Say hello",
  input_schema: %{"type" => "object"},
  handler: fn %{"name" => name}, _auth -> {:ok, "Hello #{name}!"} end
})

plug AttestoMCP.Server.Plug,
  server: server,
  path: "/mcp",
  auth: [
    config: &MyApp.Attesto.config/0,
    resource: "/mcp",
    base_url: "https://mcp.example.com"
  ]

AttestoMCP.Server.API is the stable documented facade for these startup, registration, dispatch, session, subscription, and cancellation calls; the lower-level AttestoMCP.Server module remains available for transport hosts.

Bandit is the documented development/test adapter, while the production library depends only on Plug. For a local loopback example, see examples/bandit.exs; it uses a credential-free verifier configuration and returns 401 until a host supplies a token. For stdio interop, run elixir examples/stdio.exs or call AttestoMCP.Server.Stdio.run/2.

The package-owned authenticated frozen-conformance fixture and its exact observed results are documented in CONFORMANCE.md. It is a development/test fixture only; its generated Attesto credential is never part of the library or production configuration.

Scope defaults

Tools listing uses AttestoMCP.Scopes.tools_read/0; tool execution uses tools_call/0; resources and prompt/completion reads use their corresponding AttestoMCP.Scopes helpers. Every HTTP request is reauthenticated and handles or session IDs are never authorities by themselves.

Operational notes

Pin the public origin behind a trusted proxy, use TLS in deployment, and keep credentials/proofs/private content out of logs and Telemetry. Configure the documented max_queue, stream_keepalive_ms, stream_queue_size, and concurrency/timeout limits; Plug options override server defaults for that adapter, while its effective scope_map is the single HTTP policy source. Optional task profiles are disabled for this release; their incomplete in-memory implementation cannot be enabled. A future durable host-store contract is required before either profile can be advertised.

See docs/usage.md, docs/provenance.md, docs/traceability.md, and SECURITY.md.

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