[ZERODEV / ERC-4337] Fund an on-chain escrow using a server-side session key. PRE-CONDITIONS: 1. A session key must be created first via create_session_key (returns a session_id) 2. The smart account must hold sufficient tokens 3. The escrow must be in 'Created' status SECURITY: No private keys r...
Part of the Kustodia Escrow server.
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AI agents call fund_with_session_key to retrieve information from Kustodia Escrow without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though fund_with_session_key only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"fund_with_session_key": {}
}
}See the full Kustodia Escrow policy for all 36 tools.
These attack patterns abuse exactly the kind of access fund_with_session_key gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
[ZERODEV / ERC-4337] Fund an on-chain escrow using a server-side session key. PRE-CONDITIONS: 1. A session key must be created first via create_session_key (returns a session_id) 2. The smart account must hold sufficient tokens 3. The escrow must be in 'Created' status SECURITY: No private keys required. The session_id references a server-stored session key. Executes a BATCHED UserOperation: approve + fundEscrow in ONE transaction. Gas is SPONSORED by Kustodia — no ETH needed in the smart account. For direct wallet funding (Coinbase AgentKit), use fund_web3_escrow instead.. It is categorised as a Read tool in the Kustodia Escrow MCP Server, which means it retrieves data without modifying state.
Register the Kustodia Escrow MCP server in PolicyLayer and add a rule for fund_with_session_key: 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 Kustodia Escrow. Nothing to install.
fund_with_session_key is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the fund_with_session_key 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 fund_with_session_key. 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.
fund_with_session_key is provided by the Kustodia Escrow MCP server (kustodia/escrow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 36 Kustodia Escrow tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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