Lists streams in a given project and location. For example: { parent: "projects/my-project/locations/us-central1" create_time_after: 2025-10-02T10:15:33Z create_time_before: 2025-10-03T00:00:00Z display_name: bookstore page_size: 100 running: true } will return up to 100 running streams in projec...
Part of the Mcp server.
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AI agents call list_streams to retrieve information from Mcp without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though list_streams only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"list_streams": {}
}
}See the full Mcp policy for all 10 tools.
These attack patterns abuse exactly the kind of access list_streams gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Lists streams in a given project and location. For example: { parent: "projects/my-project/locations/us-central1" create_time_after: 2025-10-02T10:15:33Z create_time_before: 2025-10-03T00:00:00Z display_name: bookstore page_size: 100 running: true } will return up to 100 running streams in projects/my-project/locations/us-central1 that were created on or after 2025-10-02T10:15:33 UTC and before 2025-10-03T00:00:00 UTC, and have "bookstore" in their display name.. It is categorised as a Read tool in the Mcp MCP Server, which means it retrieves data without modifying state.
Register the MCP server in PolicyLayer and add a rule for list_streams: 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.
list_streams 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 list_streams 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 list_streams. 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.
list_streams is provided by the MCP server (https://datastream.googleapis.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 10 Mcp tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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