Set a JSON value in Redis at a given path with an optional expiration time. Args: name: The Redis key where the JSON document is stored. path: The JSON path where the value should be set. value: The JSON value to store (as JSON string, or will be auto-converted). expire_seconds: Optional; time in...
AI agents use json_set to create or update resources in Redis MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Redis MCP Server environment.
This tool creates or modifies JSON data in Redis at a specified key and path. While modifications are reversible (the data can be overwritten or the key deleted separately), the primary action is Write. The severity is medium because misuse could corrupt application state or overwrite critical cached data, but the blast radius is limited by Redis's single-instance scope and the reversible nature of writes.
From the tool's definition Tool description states 'Set a JSON value in Redis' and 'value: The JSON value to store', indicating data creation or modification. The presence of 'expire_seconds' parameter shows optional reversible configuration.
Documented attack patterns abuse exactly the kind of access json_set gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Redis MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for json_set:
{
"version": "1",
"default": "deny",
"tools": {
"json_set": {
"limits": [
{
"counter": "json_set_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}json_set 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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Set a JSON value in Redis at a given path with an optional expiration time. Args: name: The Redis key where the JSON document is stored. path: The JSON path where the value should be set. value: The JSON value to store (as JSON string, or will be auto-converted). expire_seconds: Optional; time in seconds after which the key should expire. Returns: A success message or an error message. It is categorised as a Write tool in the Redis MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Redis MCP Server MCP server in PolicyLayer and add a rule for json_set: 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 Redis MCP Server. Nothing to install.
json_set 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 json_set 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_set. 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_set is provided by the Redis MCP Server MCP server (redis/mcp-redis). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 53 Redis MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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53 Redis MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.