Test a JavaScript regular expression against input text. POST { pattern, flags?, input }. Returns each match with its index, numbered capture groups, and named groups (up to 1000 matches with the g flag). Pure compute, no upstream.
AI agents invoke dev.regex-test to trigger actions in Mcp. 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.
The tool runs JavaScript regex evaluation (code execution) on user-supplied pattern and input. While it has no side effects or upstream calls, it executes computation based on arbitrary user-supplied patterns, placing it in the Execute category.
From the tool's definition "Test a JavaScript regular expression against input text" and "Pure compute, no upstream" — executes regex pattern matching code against provided input
Attacks that exploit this kind of access
Test a JavaScript regular expression against input text. POST { pattern, flags?, input }. Returns each match with its index, numbered capture groups, and named groups (up to 1000 matches with the g flag). Pure compute, no upstream. It is categorised as a Execute tool in the Mcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the MCP server in PolicyLayer and add a rule for dev.regex-test: 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 Mcp. Nothing to install.
dev.regex-test 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 dev.regex-test 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 dev.regex-test. 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.
dev.regex-test is provided by the MCP server (@2sio/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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