Create a NEW text node, or update an existing one (pass the same id to overwrite content/position in place — preferred over creating a duplicate). Supports cnvs markup (Markdown-ish) and Mermaid diagrams in the content. When using Mermaid, the ENTIRE content of this text node must be a single Mer...
Risk signalsAccepts raw HTML/template content (content) · High parameter count (11 properties)
Part of the Cnvs App server.
Free to start. No card required.
AI agents use add_text to create or modify resources in Cnvs App. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call add_text repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Cnvs App.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"add_text": {
"limits": [
{
"counter": "add_text_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Cnvs App policy for all 10 tools.
These attack patterns abuse exactly the kind of access add_text gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Create a NEW text node, or update an existing one (pass the same id to overwrite content/position in place — preferred over creating a duplicate). Supports cnvs markup (Markdown-ish) and Mermaid diagrams in the content. When using Mermaid, the ENTIRE content of this text node must be a single Mermaid diagram (one mermaid fenced block and nothing else — no heading, no prose before or after). If you need prose + a diagram, create two separate text nodes. postit: true renders as a yellow sticky; diagram: true renders as a framed box (2px border in the text colour, centred text) — the two are mutually exclusive. Coordinates are in board-world pixels, +x right, +y DOWN; pick a spot that does not overlap existing items (check get_preview first). Default width auto-fits content up to ~320 px; pass width for explicit wrapping (160–4096). Keep content under 100 000 chars.. It is categorised as a Write tool in the Cnvs App MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Cnvs App MCP server in PolicyLayer and add a rule for add_text: 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.
add_text 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 add_text 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 add_text. 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.
add_text 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.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.