Compact schematic SVG render of the board (typically a few kB even for dense boards). Returns both an image/svg+xml content block (you can SEE it) and the raw SVG text. CALL THIS any time you need to understand where things are — before placing new items, before deciding whether the canvas is cro...
Part of the Cnvs App server.
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AI agents call get_preview to retrieve information from Cnvs App 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 get_preview 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": {
"get_preview": {}
}
}See the full Cnvs App policy for all 10 tools.
These attack patterns abuse exactly the kind of access get_preview 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.
Compact schematic SVG render of the board (typically a few kB even for dense boards). Returns both an image/svg+xml content block (you can SEE it) and the raw SVG text. CALL THIS any time you need to understand where things are — before placing new items, before deciding whether the canvas is crowded, before picking a free region. AI-authored items get a purple border so you can tell which contributions were yours. For precise text content prefer get_board.. It is categorised as a Read tool in the Cnvs App MCP Server, which means it retrieves data without modifying state.
Register the Cnvs App MCP server in PolicyLayer and add a rule for get_preview: 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 Cnvs App. Nothing to install.
get_preview 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 get_preview 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 get_preview. 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.
get_preview is provided by the Cnvs App MCP server (https://cnvs.app/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 Cnvs App tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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