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Optional Column

The tool_policy column on mcp_sessions is optional. The SDK only writes it when you explicitly provide a toolPolicy on the session object. If you never set a policy, no migration is needed — the SDK works without the column.

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Without the Column

If you don’t run the tool_policy migration:
  • sessions.create() omits tool_policy from the INSERT
  • sessions.update() omits tool_policy from the UPDATE unless you pass it
  • sessions.get() and sessions.list() return toolPolicy: undefined, which the SDK treats as mode: 'all'

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With the Column

Uncomment the tool_policy column in the install schema when you want to persist policies: Neon — migrations/neon/20260513010000_install_mcp_sessions.sql: 
    auth_url TEXT,
    -- tool_policy JSONB -- remove the comment to enable
Supabase — migrations/supabase/20260330195700_install_mcp_sessions.sql: 
    auth_url TEXT,
    -- tool_policy JSONB -- remove the comment to enable
Run npx mcp-ts neon-init or npx mcp-ts supabase-init (or apply the migration manually) after uncommenting.

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Adding tool_policy to an existing database

If you already have sessions and want to add tool policy support later, the same SQL works for both Neon and Supabase: 
ALTER TABLE public.mcp_sessions
ADD COLUMN IF NOT EXISTS tool_policy jsonb NOT NULL DEFAULT '{"mode":"all","toolIds":[]}'::jsonb;

UPDATE public.mcp_sessions
SET tool_policy = '{"mode":"all","toolIds":[]}'::jsonb
WHERE tool_policy IS NULL;
This adds the column and backfills existing sessions with the unrestricted all policy.

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Setting a Policy

Pass toolPolicy when creating or updating a session: 
// Allowlist mode: only these two tools
await sessions.create({
  sessionId: 'sess-123',
  userId: 'user-456',
  serverUrl: 'https://mcp.example.com',
  callbackUrl: 'https://app.com/callback',
  transportType: 'streamable-http',
  toolPolicy: {
    mode: 'allowlist',
    toolIds: ['server-a::get_weather', 'server-a::send_email'],
  },
});

// Denylist mode: all tools except these
await sessions.update('user-456', 'sess-123', {
  toolPolicy: {
    mode: 'denylist',
    toolIds: ['server-a::dangerous_tool'],
  },
});

// Reset to unrestricted
await sessions.update('user-456', 'sess-123', {
  toolPolicy: { mode: 'all', toolIds: [] },
});

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Enforcing Policies at Runtime

Use the ToolPolicyGateway — it wraps a client and enforces the session’s policy before every tool call: 
import { ToolPolicyGateway } from '@mcp-ts/sdk/server';

const gateway = new ToolPolicyGateway(client, toolPolicy);

// Throws if the tool is not allowed by the policy
const result = await gateway.callTool('get_weather', { city: 'Tokyo' });
The gateway also filters listTools() results to only return allowed tools.