Add a label to a card. Use this tool to categorize a card with an existing label.
AI agents use add_label_to_card to create or update resources in Trello — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Trello environment.
This tool creates or modifies data reversibly by adding a label association to a card. It does not execute code, delete data, move money, or perform irreversible operations. The change can be undone by removing the label. The blast radius is minimal as it only affects card organization metadata within a Trello board.
From the tool's definition Tool name 'add_label_to_card' and description 'Add a label to a card. Use this tool to categorize a card with an existing label' indicate modification of card metadata by attaching an existing label.
Documented attack patterns abuse exactly the kind of access add_label_to_card gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Trello, and nothing reaches the server without passing your rules. This is the rule we recommend for add_label_to_card:
{
"version": "1",
"default": "deny",
"tools": {
"add_label_to_card": {
"limits": [
{
"counter": "add_label_to_card_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_label_to_card stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Add a label to a card. Use this tool to categorize a card with an existing label. It is categorised as a Write tool in the Trello MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Trello MCP server in PolicyLayer and add a rule for add_label_to_card: 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 Trello. Nothing to install.
add_label_to_card 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_label_to_card 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_label_to_card. 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_label_to_card is provided by the Trello MCP server (v4lheru/trello-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Trello, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
76 Trello tools catalogued and risk-classified — across an index of 43,000+ MCP servers.