feat: public MCP server — read-only context resources + refresh tool

- mcp_server.py: FastMCP server con tre risorse (session_bootstrap,
  workspace_triage, topic_index) lette dal branch context via raw URL;
  tool refresh_context triggera workflow_dispatch CI
- pyproject.toml: extra [mcp] con mcp>=1.0; entry point agent-context-mcp;
  mcp aggiunto anche a [dev]
- tests/test_mcp_server.py: 6 test su risorse e tool (fetch, no-token, success, error)
- README: sezione MCP server con configurazione Claude Code; roadmap aggiornato

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Gabrymi93

README.md

@@ -169,6 +169,55 @@ Il builder non crasha mai per dati mancanti:
 | Path locale non è un repo git | `available: false, reason: not_git_repo` |
 | `--workspace-root` non impostato | `available: false, reason: local_disabled` |
 
+## MCP Server
+
+Il repo include un server MCP pubblico che espone i tre artifact come risorse leggibili dagli agenti senza richiedere esecuzione locale del builder.
+
+### Installazione
+
+```bash
+pip install -e ".[mcp]"
+```
+
+### Avvio
+
+```bash
+agent-context-mcp
+```
+
+### Risorse esposte
+
+| URI | Contenuto |
+|---|---|
+| `context://session_bootstrap` | `session_bootstrap.md` dal branch `context` |
+| `context://workspace_triage` | `workspace_triage.json` dal branch `context` |
+| `context://topic_index` | `topic_index.json` dal branch `context` |
+
+### Tool
+
+| Tool | Descrizione |
+|---|---|
+| `refresh_context` | Triggera un nuovo build CI (richiede `GITHUB_TOKEN` con scope `workflow`) |
+
+### Configurazione Claude Code
+
+```json
+{
+  "mcpServers": {
+    "dataciviclab-context": {
+      "command": "agent-context-mcp",
+      "env": {
+        "GITHUB_TOKEN": "<token-opzionale-per-refresh>"
+      }
+    }
+  }
+}
+```
+
+Le risorse sono aggiornate automaticamente ogni 6 ore dalla CI. Il token è opzionale per la sola lettura; serve solo per `refresh_context`.
+
+Le variabili d'ambiente `ACB_REPO` e `ACB_BRANCH` permettono di puntare a un fork o a un branch diverso.
+
 ## Sviluppo
 
 ```bash
@@ -180,7 +229,8 @@ ruff check .
 ## Roadmap
 
 - **P0** — MVP: bootstrap, triage, topic index, git collector, GitHub Actions ✓
-- **P1** — Schema JSON per stabilità output; integrazione MCP `dataciviclab-state`
+- **P0.5** — MCP server pubblico: risorse read-only + tool refresh ✓
+- **P1** — Schema JSON per stabilità output; integrazione `dataciviclab-state` MCP locale
 - **P2** — Script wrapper locale; fast path in `AGENTS.md`
 
 ## Licenza

pyproject.toml

@@ -30,15 +30,20 @@ dependencies = [
 ]
 
 [project.optional-dependencies]
+mcp = [
+    "mcp>=1.0",
+]
 dev = [
     "pytest>=7.0",
     "pytest-cov>=4.0",
     "ruff>=0.1",
     "mypy>=1.0",
+    "mcp>=1.0",
 ]
 
 [project.scripts]
 agent-context = "agent_context_builder.cli:main"
+agent-context-mcp = "agent_context_builder.mcp_server:main"
 
 [tool.hatch.build.targets.wheel]
 packages = ["src/agent_context_builder"]

src/agent_context_builder/mcp_server.py

@@ -0,0 +1,99 @@
+"""Public MCP server — serves DataCivicLab context artifacts from the context branch.
+
+Exposes three read-only resources built by the CI workflow:
+  context://session_bootstrap  — session_bootstrap.md
+  context://workspace_triage   — workspace_triage.json
+  context://topic_index        — topic_index.json
+
+One optional tool:
+  refresh_context — triggers a new CI build (requires GITHUB_TOKEN with workflow scope)
+
+Configuration via environment variables:
+  ACB_REPO    GitHub repo (default: dataciviclab/agent-context-builder)
+  ACB_BRANCH  Branch where artifacts are published (default: context)
+  GITHUB_TOKEN  Required only for the refresh_context tool
+"""
+
+import os
+
+import requests
+from mcp.server.fastmcp import FastMCP
+
+_REPO = os.environ.get("ACB_REPO", "dataciviclab/agent-context-builder")
+_BRANCH = os.environ.get("ACB_BRANCH", "context")
+_RAW_BASE = f"https://raw.githubusercontent.com/{_REPO}/{_BRANCH}"
+_API_BASE = f"https://api.github.com/repos/{_REPO}"
+
+mcp = FastMCP(
+    "dataciviclab-context",
+    instructions=(
+        "DataCivicLab context artifacts, generated from GitHub every 6 hours. "
+        "Start with session_bootstrap for a quick orientation, then use "
+        "workspace_triage for machine-readable state and topic_index for "
+        "targeted exploration by topic."
+    ),
+)
+
+
+def _fetch(path: str) -> str:
+    """Fetch a file from the context branch."""
+    token = os.environ.get("GITHUB_TOKEN")
+    headers = {"Authorization": f"token {token}"} if token else {}
+    response = requests.get(f"{_RAW_BASE}/{path}", headers=headers, timeout=10)
+    response.raise_for_status()
+    return response.text
+
+
+@mcp.resource("context://session_bootstrap")
+def session_bootstrap() -> str:
+    """Orientamento rapido: repo attivi, PR aperte, discussion, stato locale, topic."""
+    return _fetch("session_bootstrap.md")
+
+
+@mcp.resource("context://workspace_triage")
+def workspace_triage() -> str:
+    """Triage machine-readable: PR, issue, discussion, stato git per repo, warning."""
+    return _fetch("workspace_triage.json")
+
+
+@mcp.resource("context://topic_index")
+def topic_index() -> str:
+    """Lookup per topic: repo rilevanti, path, prossimo passo suggerito."""
+    return _fetch("topic_index.json")
+
+
+@mcp.tool()
+def refresh_context() -> str:
+    """Triggera un nuovo build del contesto su CI.
+
+    Richiede GITHUB_TOKEN con scope workflow.
+    Gli artifact aggiornati saranno disponibili entro ~1 minuto.
+    """
+    token = os.environ.get("GITHUB_TOKEN")
+    if not token:
+        return (
+            "Errore: GITHUB_TOKEN non impostato. "
+            "Serve un token con scope 'workflow' per triggerare il build."
+        )
+
+    response = requests.post(
+        f"{_API_BASE}/actions/workflows/build-context.yml/dispatches",
+        json={"ref": "main"},
+        headers={
+            "Authorization": f"token {token}",
+            "Accept": "application/vnd.github+json",
+        },
+        timeout=10,
+    )
+    if response.status_code == 204:
+        return "Build triggerato. Gli artifact saranno aggiornati entro ~1 minuto."
+    return f"Errore: {response.status_code} — {response.text}"
+
+
+def main() -> None:
+    """Entry point per l'MCP server."""
+    mcp.run()
+
+
+if __name__ == "__main__":
+    main()

tests/test_mcp_server.py

@@ -0,0 +1,83 @@
+"""Tests for MCP server resources and tools."""
+
+from unittest.mock import MagicMock, patch
+
+
+def _mock_response(text: str, status: int = 200):
+    m = MagicMock()
+    m.text = text
+    m.status_code = status
+    m.raise_for_status.return_value = None
+    return m
+
+
+def test_session_bootstrap_resource():
+    """session_bootstrap fetches session_bootstrap.md from context branch."""
+    from agent_context_builder.mcp_server import session_bootstrap
+
+    with patch("agent_context_builder.mcp_server.requests.get") as mock_get:
+        mock_get.return_value = _mock_response("# Session Bootstrap\n")
+        result = session_bootstrap()
+
+    assert "Session Bootstrap" in result
+    called_url = mock_get.call_args[0][0]
+    assert "session_bootstrap.md" in called_url
+    assert "context" in called_url
+
+
+def test_workspace_triage_resource():
+    """workspace_triage fetches workspace_triage.json from context branch."""
+    from agent_context_builder.mcp_server import workspace_triage
+
+    with patch("agent_context_builder.mcp_server.requests.get") as mock_get:
+        mock_get.return_value = _mock_response('{"open_prs": 2}')
+        result = workspace_triage()
+
+    assert "open_prs" in result
+    assert "workspace_triage.json" in mock_get.call_args[0][0]
+
+
+def test_topic_index_resource():
+    """topic_index fetches topic_index.json from context branch."""
+    from agent_context_builder.mcp_server import topic_index
+
+    with patch("agent_context_builder.mcp_server.requests.get") as mock_get:
+        mock_get.return_value = _mock_response('{"topics": {}}')
+        result = topic_index()
+
+    assert "topics" in result
+    assert "topic_index.json" in mock_get.call_args[0][0]
+
+
+def test_refresh_context_no_token(monkeypatch):
+    """refresh_context returns error message when GITHUB_TOKEN not set."""
+    from agent_context_builder.mcp_server import refresh_context
+
+    monkeypatch.delenv("GITHUB_TOKEN", raising=False)
+    result = refresh_context()
+
+    assert "GITHUB_TOKEN" in result
+
+
+def test_refresh_context_success(monkeypatch):
+    """refresh_context triggers workflow dispatch and reports success."""
+    from agent_context_builder.mcp_server import refresh_context
+
+    monkeypatch.setenv("GITHUB_TOKEN", "fake-token")
+    with patch("agent_context_builder.mcp_server.requests.post") as mock_post:
+        mock_post.return_value = _mock_response("", status=204)
+        result = refresh_context()
+
+    assert "triggerato" in result.lower()
+
+
+def test_refresh_context_api_error(monkeypatch):
+    """refresh_context reports API errors without raising."""
+    from agent_context_builder.mcp_server import refresh_context
+
+    monkeypatch.setenv("GITHUB_TOKEN", "fake-token")
+    with patch("agent_context_builder.mcp_server.requests.post") as mock_post:
+        mock_post.return_value = _mock_response("Forbidden", status=403)
+        result = refresh_context()
+
+    assert "403" in result