Import a HAR file from disk into a new persisted session for querying, findings, and replay.
AI agents use proxy_import_har to create or update resources in Proxy — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Proxy environment.
Importing a HAR file into a persisted session is a Write operation: it creates or modifies stored state in the proxy system. The severity is high because HAR files contain sensitive data (credentials, API keys, session tokens, request/response bodies), and importing them into a live MITM proxy that supports replay and modification creates risk of credential exposure, session hijacking, or replay attacks.
From the tool's definition Tool description states it 'Import[s] a HAR file from disk into a new persisted session' — this creates persistent stored data.
Documented attack patterns abuse exactly the kind of access proxy_import_har gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Proxy, and nothing reaches the server without passing your rules. This is the rule we recommend for proxy_import_har:
{
"version": "1",
"default": "deny",
"tools": {
"proxy_import_har": {
"limits": [
{
"counter": "proxy_import_har_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}proxy_import_har stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Import a HAR file from disk into a new persisted session for querying, findings, and replay. It is categorised as a Write tool in the Proxy MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Proxy MCP server in PolicyLayer and add a rule for proxy_import_har: 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 Proxy. Nothing to install.
proxy_import_har 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 proxy_import_har 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 proxy_import_har. 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.
proxy_import_har is provided by the Proxy MCP server (yfe404/proxy-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Proxy, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
89 Proxy tools catalogued and risk-classified — across an index of 43,000+ MCP servers.