Build and test regex patterns. POST /build creates a regex from a pattern string or components. POST /test validates a pattern against test strings. Useful for generating and debugging regular expressions.
AI agents invoke regex_builder to trigger actions in APIMesh MCP Server. 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 regex_builder does not directly execute shell commands or arbitrary code, it triggers regex engine execution with user-controlled input, which can cause denial of service, infinite loops, or unexpected computational behavior. This falls under Execute rather than Write because the effects are triggered computational operations, not data modification.
From the tool's definition Tool performs regex pattern building and testing via POST endpoints that accept user-supplied pattern strings and test inputs.
Attacks that exploit this kind of access
Build and test regex patterns. POST /build creates a regex from a pattern string or components. POST /test validates a pattern against test strings. Useful for generating and debugging regular expressions. It is categorised as a Execute tool in the APIMesh MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the APIMesh MCP Server MCP server in PolicyLayer and add a rule for regex_builder: 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 APIMesh MCP Server. Nothing to install.
regex_builder 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 regex_builder 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 regex_builder. 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.
regex_builder is provided by the APIMesh MCP Server MCP server (mbeato/apimesh). 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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