How to Implement MCP File Access Control

MCP file access control applies role-based access control to Fastio workspaces so agents only touch files and operations they're authorized for. Five roles define what's allowed: owner (full control), admin (manage members and settings), member (read/write/share), guest (read/limited share), view (read-only). Permissions cascade from organization down to workspace, folder, and file. Each level inherits from above but can be overridden. An org member role grants workspace access, but a folder view role blocks edits there. File locks add a second layer of protection for concurrent writes. The MCP tools handle auth via session calls, no manual token passing required. Helpful references: Fastio Workspaces, Fastio Collaboration, Fastio AI, MCP Server.

Multi-agent workflows mean several LLMs sharing the same files. Without access controls, one agent's bad prompt can overwrite another's output or pull data it has no business seeing. RBAC limits the blast radius. An analysis agent gets view access; a writer gets member rights. Neither can touch what it doesn't need. Pair that with file locks for concurrent edits: acquire before modifying, release when done. Audit logs record every action with actor, timestamp, and operation. Filter by user, entity, or time range when you need to trace what happened.

Set up RBAC from scratch in these steps. Test each layer before moving to production.

Step 1: Create Agent Account

Agents sign up via auth action signup. This assigns the free agent plan: multiple storage, multiple credits/month, no credit card.

{
  "tool": "auth",
  "action": "signup",
  "first_name": "RBAC",
  "last_name": "Agent",
  "email": "rbac-agent@example.com",
  "password": "SecurePass123!"
}

Check status: auth action status. Verify email: auth action email-verify with code.

Step 2: Create Organization

Use org action create with billing_plan: "agent" for free tier.

{
  "tool": "org",
  "action": "create",
  "billing_plan": "agent",
  "name": "SecureAgentOrg"
}

List orgs: org action list and discover-external.

Step 3: Create Workspace

{
  "tool": "org",
  "action": "create-workspace",
  "org_id": "org_1234567890123456789",
  "name": "rbac-demo",
  "intelligence": true
}

Enable workflow if needed: workspace action enable-workflow.

Step 4: Add Members and Assign Roles

Invite via member action add. Roles: owner (full), admin (manage), member (rw/share), guest (r/limited), view (r).

{
  "tool": "member",
  "action": "add",
  "entity_type": "workspace",
  "entity_id": "ws_9876543210987654321",
  "profile_type": "user",
  "profile_id": "user_4567890123456789012",
  "role": "member"
}

For org: entity_type: "org". List: member action list.

Step 5: Test Permissions

As test agent, try storage action list with context_permissions: true. Expect multiple on denied ops.

Common pitfall: External orgs -- use org action discover-external.

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Permissions cascade from organization to file but allow overrides at each level. Use storage action permissions-set for node-specific rules.

First, list effective perms: context_permissions: true in storage list/details.

{
  "tool": "storage",
  "action": "list",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "node_id": "root",
  "context_permissions": true,
  "include_folders": true
}

Set folder perms (override inheritance):

{
  "tool": "storage",
  "action": "permissions-set",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "node_id": "folder_xyz",
  "permissions": {
    "read": ["member:user456"],
    "write": ["admin:user789"],
    "delete": [],
    "share": ["owner:*"]
  }
}

Sub-workspaces offer isolation: create child workspaces for teams. Locks add runtime safety. Acquire before batch edits.

In multi-agent systems, locks prevent conflicts during edits. One agent holds the lock while others wait or read-only.

Workflow: Check status (storage details), acquire if free, edit, release. Locks auto-expire after multiple minutes inactivity.

Acquire:

{
  "tool": "storage",
  "action": "lock-acquire",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "node_id": "fileabc123"
}

Status check:

{
  "tool": "storage",
  "action": "details",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "node_id": "fileabc123"
}

Release:

{
  "tool": "storage",
  "action": "lock-release",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "node_id": "fileabc123"
}

If acquire fails (locked), poll status or notify via webhook. Locks are per-file, non-blocking for reads.

If your agent crashes while holding a lock, the TTL auto-expiry is your safety net, but size it carefully. For a process that normally completes in 90 seconds, a 5-minute TTL is enough headroom without blocking another agent for long if something goes wrong.

Logs track every action: uploads, downloads, perm changes, member adds, locks.

List recent:

{
  "tool": "event",
  "action": "activity-list",
  "context_type": "workspace",
  "workspace_id": "ws98765432109876543",
  "limit": 100,
  "offset": 0,
  "filter": {
    "actor_profile_type": "user",
    "action": "upload"
  }
}

Filter examples:

• User-specific: "filter": {"actor_profile_id": "user456"}
• Time range: "start_ts": 1700000000, "end_ts": 1704067200
• Action: "filter": {"action": "permission-change"}

Poll for real-time: event action activity-poll. Export to CSV for analysis.

Logs aid compliance: prove who accessed what when.

• Assign minimum roles. View for readers, member for editors. Don't give an agent admin because it's convenient.
• Query event activity-list weekly. Set up webhooks to alert on anomalies so you're not reviewing logs reactively.
• Build workspaces as agents, then transfer to humans with org transfer-token-create when setup is done.
• Enable MFA on all accounts. Agents authenticate via PKCE.
• Use PKCE with scope_type: "workspace" for narrow, temporary access.
• Keep lock durations short. Auto-expiry is the fallback, not the plan.
• Duplicate the prod workspace for staging. Simulate failures before they happen in production.
• Export audit logs to external storage. On-platform logs are convenient; immutable off-platform copies are what compliance actually requires.
• Rotate API keys quarterly via auth api-key-create.

Start with one workspace and two agents with distinct roles before scaling up. Once that pairing works in staging, replicate the permission structure. Keep a change log: what role, which agent, why — so you can reverse a change in minutes when something breaks.

403 Permission Denied

View/guest roles block writes/deletes. Fix: member list, then update-role. Verify: storage list context_permissions: true.

Lock Conflicts

Acquire fails if held. Fix: storage details for holder/expiry. Poll or force release if owner.

Scope Errors (PKCE)

Token lacks entity access. Fix: Re-login with scope_type: "all_workspaces".

External Org Missing

org list misses invites. Fix: org discover-external.

Token Expiry

401 after 1hr. Fix: auth signin.

Pro Tip: Staging workspace for tests. Logs first for diagnosis.

When an agent hits a 403, resist jumping straight to role upgrades. Pull the audit log first to confirm the exact resource and action that failed. Half the time it's a wrong entity_id in the member add call, not a missing permission.

Scenario: Research (view), Writer (member), Reviewer (admin) on "Q4 Report" workspace.

1. Owner creates ws, invites:

   • Research agent: member role on /data folder (view only).
   • Writer: member on /drafts.
   • Reviewer: admin on ws.

2. Research uploads data (storage upload), locks folder.

3. Writer reads data, generates draft, locks file.

4. Reviewer audits logs (event activity-list), approves.

Code skeleton:

// Invite research
{"tool":"member","action":"add","entity_type":"folder","entity_id":"data_folder","profile_id":"research_agent","role":"view"}

Locks ensure no overwrites. Logs prove chain of custody.

Before running this with real files, test the full lock-acquire-edit-release cycle in a scratch workspace with dummy data. A lock left open by a crashed agent can block the next run, so confirm your TTL is short enough that auto-expiry clears it before any retry fires.

OpenClaw agents use Fastio via ClawHub skill: clawhub install dbalve/fast-io.

multiple tools mirror MCP: storage, shares, AI chat.

RBAC applies: Install grants access per agent perms.

Example workflow: Claw agent lists ws files (storage list), checks perms, uploads if member.

Zero-config: No env vars. Works with any LLM.

Link: OpenClaw Fastio.

• Dynamic roles: Script role assignment based on task (view for analysis, member for write).
• Webhooks + RBAC: Notify on perm changes (webhook create).
• Scoped PKCE: pkce-login scope_type="workspace" for temp agents.
• Compliance export: event activity-list > JSON to S3.

Assign roles dynamically when agents need temporary write access rather than leaving elevated permissions in place permanently. Webhook notifications on permission changes are cheap to set up and save debugging time later.