Claim a free marketplace item for the signed-in user, copying it into their inventory. Required before adding the item to a room. Paid items must use create-checkout (not yet exposed via MCP). Idempotent: returns ALREADY_CLAIMED if the user already owns it.
AI agents use claim_marketplace_item to create or update resources in Portals — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Portals environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
itemId | string | Yes | The id of the marketplace item to claim. |
Parameters from the server's own tool schema.
This tool modifies user inventory by claiming (acquiring) a marketplace item, which is a Write operation—it creates or modifies data reversibly. The severity is medium rather than high because the blast radius of claiming an unwanted free item is limited (the user can presumably unclaim or delete it), and it only affects free items, not paid transactions.
From the tool's definition The tool 'claim_marketplace_item' performs a copy operation into user inventory ('copying it into their inventory'). It creates a new ownership state for the user via a claim action, which is a reversible modification of user data/inventory state.
Attacks that exploit this kind of access
Claim a free marketplace item for the signed-in user, copying it into their inventory. Required before adding the item to a room. Paid items must use create-checkout (not yet exposed via MCP). Idempotent: returns ALREADY_CLAIMED if the user already owns it. It is categorised as a Write tool in the Portals MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
claim_marketplace_item accepts 1 parameter: itemId. Required: itemId. The full parameter table on this page comes from the server's own tool schema.
Register the Portals MCP server in PolicyLayer and add a rule for claim_marketplace_item: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Portals. Nothing to install.
claim_marketplace_item is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the claim_marketplace_item rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for claim_marketplace_item. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
claim_marketplace_item is provided by the Portals MCP server (portals-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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