frontmcp-authorities

FrontMCP Authorities

Built-in RBAC/ABAC/ReBAC authorization system for FrontMCP entry types. Each flow has native checkEntryAuthorities and filterByAuthorities stages that enforce access control policies declared via the authorities field on entry decorators. Configured via @FrontMcp({ authorities: { claimsMapping, profiles, scopeMapping } }) — no plugin needed. Flow stages handle enforcement, and developers can hook into them with Will, Did, and Around decorators. Supports named profiles for reuse, JWT claims mapping for any identity provider, inline policies with roles/permissions/attributes/relationships, and composable combinators (allOf, anyOf, not).

When to Use This Skill

Must Use

• Adding role-based or permission-based access control to tools, resources, prompts, or skills
• Restricting MCP entry visibility based on the caller's JWT claims
• Enforcing tenant isolation (ABAC) or relationship checks (ReBAC) on entries
• Gating which skills a caller can discover and load (@Skill({ authorities }))

Recommended

• Setting up a multi-tenant server where different tenants see different tools
• Building an admin vs. user distinction across your MCP surface
• Combining multiple authorization models (e.g., RBAC + ABAC) on the same entry

Skip When

• You only need authentication (login/token validation) without authorization (see frontmcp-config / configure-auth)
• You are building a public server with no access restrictions (use mode: 'public')
• You need OAuth scopes at the transport level, not entry-level policies (see configure-auth-modes)

Decision: Use this skill whenever you need to control who can access which entries based on roles, permissions, attributes, or relationships.

CRITICAL: Ask About JWT Shape First

Before writing any authorities configuration, the coding agent MUST ask the developer:

"What identity provider (IdP) are you using, and what does your JWT payload look like? I need to know where roles, permissions, and tenant ID are located in the claims."

Why this matters: Every IdP places roles and permissions in different JWT claim paths. Auth0 uses namespaced URIs (https://myapp.com/roles), Keycloak nests them under realm_access.roles, Okta uses groups, Cognito uses cognito:groups, and Frontegg uses flat roles/permissions. Writing claimsMapping without knowing the actual token shape will produce silent authorization failures where every user is denied.

What to collect before proceeding:

1. Identity provider name (Auth0, Keycloak, Okta, Cognito, Frontegg, custom)
2. A sample decoded JWT payload (redacted sensitive values)
3. The claim path for roles (e.g., realm_access.roles)
4. The claim path for permissions (e.g., permissions or scope)
5. The claim path for tenant/org ID if multi-tenant (e.g., org_id, tenantId)

See references/claims-mapping.md for IdP-specific claim paths.

Prerequisites

• FrontMCP SDK installed (@frontmcp/sdk)
• @frontmcp/auth available (peer dependency of SDK, provides all authorities types)
• An authentication mode configured (see frontmcp-config / configure-auth-modes) so that authInfo is populated on incoming requests
• Knowledge of the developer's JWT token structure (see critical section above)

Steps

Step 1: Add the Authorities Config

Add the authorities field to your @FrontMcp decorator. No plugin import needed — authorities is a built-in framework feature.

import { FrontMcp } from '@frontmcp/sdk';

@FrontMcp({
  info: { name: 'my-server', version: '1.0.0' },
  authorities: {
    // configured in next steps
  },
})
export class MyServer {}

Step 2: Configure JWT Claims Mapping

Set claimsMapping to tell the engine where roles, permissions, and user/tenant identifiers live in your IdP's JWT. Each value is a dot-path into the decoded JWT claims object.

// Keycloak example — in @FrontMcp({ authorities: { ... } })
authorities: {
  claimsMapping: {
    roles: 'realm_access.roles',
    permissions: 'resource_access.my-client.roles',
    tenantId: 'org_id',
    userId: 'sub',
  },
}

// Auth0 example
authorities: {
  claimsMapping: {
    roles: 'https://myapp.com/roles',
    permissions: 'permissions',
    tenantId: 'org_id',
  },
}

If no claimsMapping is provided, the engine falls back to (in order):

• roles: authInfo.user.roles → authInfo.extra.authorization.scopes → []
• permissions: authInfo.user.permissions → []

The OAuth-scopes-as-roles fallback means a token with no roles claim but with scope: "admin read" will be treated as having roles: ['admin', 'read']. Configure explicit claimsMapping.roles to opt out. For non-standard token shapes, use claimsResolver instead (see Common Patterns below).

Step 3: Register Named Profiles

Profiles let you define reusable authorization policies and reference them by name in decorators. Register them in the profiles field.

// In @FrontMcp({ authorities: { ... } })
authorities: {
  claimsMapping: { roles: 'realm_access.roles', permissions: 'scope' },
  profiles: {
    admin: {
      roles: { any: ['admin', 'superadmin'] },
    },
    authenticated: {
      attributes: {
        conditions: [{ path: 'user.sub', op: 'exists', value: true }],
      },
    },
    matchTenant: {
      attributes: {
        conditions: [
          { path: 'claims.org_id', op: 'eq', value: { fromInput: 'tenantId' } },
        ],
      },
    },
    editor: {
      permissions: { any: ['content:write', 'content:publish'] },
    },
  },
}

For type-safe profile names, augment the global interface:

declare global {
  interface FrontMcpAuthorityProfiles {
    admin: true;
    authenticated: true;
    matchTenant: true;
    editor: true;
  }
}

Step 4: Add Authorities to Entries

Use the authorities field on any entry decorator (@Tool, @Resource, @Prompt, @Skill). Three forms are supported:

String (profile reference):

@Tool({ name: 'delete_user', authorities: 'admin' })
export default class DeleteUserTool extends ToolContext { ... }

String array (multiple profiles, AND semantics):

@Tool({ name: 'update_tenant_settings', authorities: ['authenticated', 'matchTenant'] })
export default class UpdateTenantSettingsTool extends ToolContext { ... }

Inline policy object:

@Tool({
  name: 'publish_content',
  authorities: {
    roles: { any: ['editor', 'admin'] },
    permissions: { all: ['content:publish'] },
  },
})
export default class PublishContentTool extends ToolContext { ... }

Combinators for complex policies:

@Tool({
  name: 'sensitive_action',
  authorities: {
    allOf: [
      { roles: { any: ['admin'] } },
      { attributes: { conditions: [{ path: 'env.NODE_ENV', op: 'eq', value: 'production' }] } },
    ],
  },
})
export default class SensitiveActionTool extends ToolContext { ... }

Async guards (one-shot DB/Redis/API checks):

For dynamic, async authorization that does not warrant a reusable custom evaluator, use the guards field. Each guard receives the same AuthoritiesEvaluationContext and returns true on grant, or false/a denial string on deny. Guards run in sequence and combine with other policy fields via operator (default AND).

import type { AuthorityGuardFn } from '@frontmcp/auth';

const requireActiveSubscription: AuthorityGuardFn = async (ctx) => {
  const active = await db.isSubscriptionActive(ctx.user.sub);
  return active ? true : 'subscription is not active';
};

@Tool({
  name: 'premium_feature',
  authorities: {
    roles: { any: ['user'] },
    guards: [requireActiveSubscription],
  },
})
export default class PremiumFeatureTool extends ToolContext { ... }

Use guards for one-off async checks; promote to a registered custom evaluator when the same logic is reused across many entries (see references/custom-evaluators.md).

Optional: Map Denials to OAuth Scope Challenges (scopeMapping)

If your transport layer issues OAuth scope challenges (RFC 6750 insufficient_scope), declare a scopeMapping so authority denials are converted into the right WWW-Authenticate challenge with the required scopes. Mapping is explicit only — no automatic permission-to-scope inference.

authorities: {
  scopeMapping: {
    roles: { admin: ['admin:all'] },
    permissions: { 'repo:write': ['repo'] },
    profiles: { admin: ['admin:all'] },
  },
}

When a request is denied because the user lacks role admin, the response surfaces the admin:all scope as the required challenge.

Optional: Extract Custom Auth Context Fields (pipes)

pipes are functions that run during auth context construction and merge their output into FrontMcpAuthContext. Use them to extract custom typed fields from JWT claims so they are available to your tools as strongly typed accessors. Declare the resulting fields by augmenting ExtendFrontMcpAuthContext:

A pipe receives the raw JWT claims (a Readonly<Record<string, unknown>>) and returns a Partial<ExtendFrontMcpAuthContext> (sync or async). It does not receive the AuthInfo envelope — there is no .user accessor on the input.

// Pipe signature (defined inline; do not import — AuthContextPipe is not
// re-exported from `@frontmcp/auth`):
//   (claims: Readonly<Record<string, unknown>>) =>
//     Partial<ExtendFrontMcpAuthContext> | Promise<Partial<ExtendFrontMcpAuthContext>>

const tenantPipe = (claims: Readonly<Record<string, unknown>>) => ({
  tenantId: claims['tenantId'] as string | undefined,
});

declare global {
  interface ExtendFrontMcpAuthContext {
    tenantId?: string;
  }
}

// In @FrontMcp({ authorities: { ... } })
authorities: {
  pipes: [tenantPipe],
}

Skill Authorities (@Skill({ authorities }))

authorities on @Skill is enforced exactly like the other entry types, across every surface a skill is served from:

• Deny on load/read — loading a gated skill the caller can't access throws AuthorityDeniedError (MCP code -32003), the same as a denied tools/call. Covers skills/load (MCP), skill://<path>/SKILL.md and skill://<path>/<file> reads (SEP-2640), and GET /skills/{id} (HTTP).
• Filter on discovery — gated skills the caller can't access are removed from skills/search / skills/list (MCP), the skill://index.json discovery index and skill-path autocomplete (SEP-2640), and GET /skills (HTTP).

@Skill({ name: 'review-pr', description: '…', instructions: '…' })            // open to all
@Skill({ name: 'internal-runbook', description: '…', instructions: '…',
         authorities: 'admin' })                                              // admins only

Two limitations to design around:

• List-time filtering is role/permission/claims-only. Discovery runs without request input, so { fromInput: '…' } ABAC/ReBAC policies can't be evaluated when filtering and will hide the skill from discovery. Use role/permission/claims authorities for discoverable skills; input-dependent policies still enforce at load time. (Same limitation applies to tools/resources/prompts.)
• HTTP skills discovery is fail-closed. The Skills HTTP API uses a binary api-key/bearer gate with no claims, so gated skills are hidden from GET /skills and denied on GET /skills/{id} regardless of the bearer. Serve gated skills over an MCP transport for claims-based access. Ungated skills are unaffected.

Boot-time fail-fast covers skills too: a @Skill with authorities but no configured authorities engine fails server startup with AuthConfigurationError, exactly like a tool/resource/prompt/agent.

Scenario Routing Table

Common Patterns

Verification Checklist

Configuration

• authorities: { ... } is set on the @FrontMcp decorator
• claimsMapping paths match the actual JWT token structure from your IdP
• All profile names referenced in authorities: 'name' are registered in profiles
• Authentication mode is configured (not public) so authInfo is populated
• If using ReBAC, relationshipResolver is provided in plugin options

Runtime

• Unauthenticated requests to protected entries receive a denial error
• Users with the correct roles/permissions can access their entries
• tools/list response omits entries the caller is not authorized to see
• ABAC conditions with { fromInput: ... } resolve correctly from tool arguments
• Custom evaluators return proper AuthoritiesResult objects

Type Safety

• FrontMcpAuthorityProfiles is augmented for type-safe profile references
• @frontmcp/auth is imported so the authorities field is available on decorators

Troubleshooting

Examples

This skill currently exposes only references; see references/ for guidance.

Accessing This Skill

Skills are distributed as plain SKILL.md files plus a sibling references/ and examples/ tree, so consumers can pick whichever access mode fits:

The catalog itself is not an MCP server. The skill:// URIs only resolve when a server has been configured to host this skill.

Reference

• Auth Architecture — Full three-layer model: server auth, auth providers, authorities, vault, scope challenges
• Authorities Documentation — RBAC/ABAC/ReBAC details, profiles, combinators, hooking
• Source: libs/auth/src/authorities/ (engine, types, evaluators), flow stages in libs/sdk/src/tool/flows/, libs/sdk/src/resource/flows/, libs/sdk/src/prompt/flows/, libs/sdk/src/agent/flows/
• Related skills: frontmcp-config, frontmcp-development, frontmcp-extensibility