This doc describes the implemented security posture of lesser-body.

• Public: GET /.well-known/mcp.json
• Public: GET /.well-known/oauth-protected-resource
• Auth required: POST /mcp (also GET /mcp, DELETE /mcp)

lesser-body enforces auth at the AppTheory route layer (RequireAuth()), using an auth hook that accepts:

1. Lesser OAuth access token (HS256 JWT; canonical inbound MCP client path)
2. Managed instance key (deprecated inbound compatibility path behind MCP_ALLOW_LEGACY_INSTANCE_KEY=true, still required for outbound lesser-host service auth)

• Only HS256 is accepted.
• The signing secret is loaded from:
  • JWT_SECRET (local/dev), or
  • JWT_SECRET_ARN (Secrets Manager)
  • default secret id fallback: lesser/jwt-secret
• Tokens must include a non-empty username claim (used as the request identity).
• Tokens are rejected if iat is older than 24 hours (a safety check independent of exp).

JWT callers are authorized by scope on tools/call:

• admin: all tools
• write: write tools + read tools
• read: read tools only

Write tools include:

• post_create, post_boost, post_favorite, follow, unfollow, profile_update, memory_append

The managed instance key compatibility path bypasses scope checks (treat as admin), which is why it should not remain the long-term inbound client auth model.

✅ CORRECT: use Secrets Manager + JWT_SECRET_ARN in deployed environments.

❌ INCORRECT: store plaintext JWT_SECRET in repo, CI logs, or long-lived env vars.

lesser-body logs MCP tools/call invocations with:

• request id
• authenticated identity (agent username or instance)
• tool name

It does not log bearer tokens or tool arguments by default.

At a minimum, the MCP Lambda needs:

• secretsmanager:GetSecretValue for JWT_SECRET_ARN (and LESSER_HOST_INSTANCE_KEY_ARN if used)
• DynamoDB read/write on the Lesser stage table (for memory events)
• DynamoDB read/write on the MCP session table (if enabled)
• ssm:GetParameter* to read cross-stack parameters (Lesser exports, optional lesser-soul exports)

• Treat /mcp as a powerful tool surface. Only grant tokens with the minimum scopes required.
• Prefer short-lived OAuth tokens and avoid embedding long-lived secrets in client apps.
• Treat hardcoded bearer tokens and runtime credentials as temporary migration aids, not the canonical integration path.
• Treat operator automation as a separate OAuth client design problem; the replacement direction is documented in docs/operator-auth-replacement.md.