Assert that current URL contains a pattern or matches regex.
AI agents call assert_url_matches to retrieve information from Visual Annotation 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 checks the current URL against a pattern or regex. It performs a read/query operation with no side effects, modifications, or executions. It is purely a validation/assertion tool.
From the tool's definition Assert that current URL contains a pattern or matches regex
Attacks that exploit this kind of access
Assert that current URL contains a pattern or matches regex. It is categorised as a Read tool in the Visual Annotation MCP MCP Server, which means it retrieves data without modifying state.
Register the Visual Annotation MCP server in PolicyLayer and add a rule for assert_url_matches: 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 Visual Annotation MCP. Nothing to install.
assert_url_matches 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 assert_url_matches 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 assert_url_matches. 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.
assert_url_matches is provided by the Visual Annotation MCP server (mstocker1/visual_annotation_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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