Analyze the size breakdown of JSON data using a shape object to determine granularity. Returns size information in bytes for each specified field, mirroring the shape structure but with size values instead of data.
AI agents call json_dry_run to retrieve information from JSON Filter MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only reads and analyzes JSON data to report size metrics. It has no side effects, does not modify any data, and merely returns metadata (byte sizes) about the structure. Misuse potential is minimal as it only exposes size information, not the actual data contents.
From the tool's definition Analyze the size breakdown of JSON data... Returns size information in bytes for each specified field... with size values instead of data
Documented attack patterns abuse exactly the kind of access json_dry_run gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and JSON Filter MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for json_dry_run:
{
"version": "1",
"default": "deny",
"tools": {
"json_dry_run": {}
}
}json_dry_run is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Analyze the size breakdown of JSON data using a shape object to determine granularity. Returns size information in bytes for each specified field, mirroring the shape structure but with size values instead of data. It is categorised as a Read tool in the JSON Filter MCP MCP Server, which means it retrieves data without modifying state.
Register the JSON Filter MCP server in PolicyLayer and add a rule for json_dry_run: 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 JSON Filter MCP. Nothing to install.
json_dry_run 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 json_dry_run 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 json_dry_run. 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.
json_dry_run is provided by the JSON Filter MCP server (kehvinbehvin/json-mcp-filter). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from JSON Filter MCP, 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.
3 JSON Filter MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.