AI agents invoke dynamic_runtime_call to trigger actions in Substrate MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool runs runtime API calls on a Substrate blockchain, which can trigger arbitrary state changes or blockchain operations depending on the caller's arguments. While not inherently destructive or financial, it meets the Execute category definition as it triggers external operations with argument-dependent effects.
From the tool's definition Tool name 'dynamic_runtime_call' and description 'Execute a runtime API call' explicitly indicate code/API execution capability.
Documented attack patterns abuse exactly the kind of access dynamic_runtime_call gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Substrate MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for dynamic_runtime_call:
{
"version": "1",
"default": "deny",
"tools": {
"dynamic_runtime_call": {
"limits": [
{
"counter": "dynamic_runtime_call_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}dynamic_runtime_call stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Execute a runtime API call. It is categorised as a Execute tool in the Substrate MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Substrate MCP Server MCP server in PolicyLayer and add a rule for dynamic_runtime_call: 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 Substrate MCP Server. Nothing to install.
dynamic_runtime_call is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the dynamic_runtime_call 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 dynamic_runtime_call. 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.
dynamic_runtime_call is provided by the Substrate MCP Server MCP server (thomasmarches/substrate-mcp-rs). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Substrate MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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13 Substrate MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.