Send a state-changing transaction to a deployed contract (cast send)
Risk signalsHigh parameter count (17 properties)
Part of the Foundry Zksync server.
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AI agents use cast_send to create or modify resources in Foundry Zksync. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call cast_send repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Foundry Zksync.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"cast_send": {
"limits": [
{
"counter": "cast_send_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Foundry Zksync policy for all 21 tools.
These attack patterns abuse exactly the kind of access cast_send gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Send a state-changing transaction to a deployed contract (cast send). It is categorised as a Write tool in the Foundry Zksync MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Foundry Zksync MCP server in PolicyLayer and add a rule for cast_send: 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 Foundry Zksync. Nothing to install.
cast_send 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 cast_send 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 cast_send. 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.
cast_send is provided by the Foundry Zksync MCP server (foundry-zksync-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 21 Foundry Zksync tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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