Test a JSONata expression with context
AI agents invoke testJSONata to trigger actions in mcpGraph. 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.
While 'test' implies evaluation/read semantics, executing a JSONata expression is running code/logic against input data. JSONata expressions can perform complex transformations and computations. This falls under Execute since it runs an expression/script. Severity is medium as it's sandboxed to expression evaluation but could be misused to probe data or cause unintended transformations in a pipeline context.
From the tool's definition 'Test a JSONata expression with context' — executes a JSONata expression (a query/transformation language) against provided data
Documented attack patterns abuse exactly the kind of access testJSONata gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and mcpGraph, and nothing reaches the server without passing your rules. This is the rule we recommend for testJSONata:
{
"version": "1",
"default": "deny",
"tools": {
"testJSONata": {
"limits": [
{
"counter": "testjsonata_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}testJSONata 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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Test a JSONata expression with context. It is categorised as a Execute tool in the mcpGraph MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the mcpGraph MCP server in PolicyLayer and add a rule for testJSONata: 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 mcpGraph. Nothing to install.
testJSONata 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 testJSONata 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 testJSONata. 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.
testJSONata is provided by the mcpGraph MCP server (teamsparkai/mcpgraph). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from mcpGraph, 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.
13 mcpGraph tools catalogued and risk-classified — across an index of 43,000+ MCP servers.