INTERNAL SYSTEM TOOL. DO NOT CALL. This tool is strictly for the frontend UI iframe to execute native filesystem saves. You (the AI model) do not have access to the base64 canvas data required to use this tool. Any attempt by the AI to call this tool will fail. Ignore this tool entirely.
AI agents use save-chart to create or update resources in Vonage Mcp Server Api Bindings — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Vonage Mcp Server Api Bindings environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
filename | string | Yes | The name of the file to save, including the .png extension |
base64Data | string | Yes | The base64 encoded PNG image string |
Parameters from the server's own tool schema.
The tool performs a Write operation by saving chart data to the filesystem. Although the description warns this is an internal UI tool that AI models cannot successfully use (lacking required base64 canvas data), the underlying capability is a reversible write operation.
From the tool's definition Tool name is 'save-chart' and description explicitly states it performs 'filesystem saves'. This involves writing/persisting data to disk.
Risk signalsAccepts file system path (filename)
Attacks that exploit this kind of access
INTERNAL SYSTEM TOOL. DO NOT CALL. This tool is strictly for the frontend UI iframe to execute native filesystem saves. You (the AI model) do not have access to the base64 canvas data required to use this tool. Any attempt by the AI to call this tool will fail. Ignore this tool entirely. It is categorised as a Write tool in the Vonage Mcp Server Api Bindings MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
save-chart accepts 2 parameters: filename, base64Data. Required: filename, base64Data. The full parameter table on this page comes from the server's own tool schema.
Register the Vonage Mcp Server Api Bindings MCP server in PolicyLayer and add a rule for save-chart: 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 Vonage Mcp Server Api Bindings. Nothing to install.
save-chart is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the save-chart 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 save-chart. 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.
save-chart is provided by the Vonage Mcp Server Api Bindings MCP server (@vonage/vonage-mcp-server-api-bindings). 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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