Add a comment to a card. Use this tool to add notes or feedback to a card.
AI agents use add_comment 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.
Adding a comment is a reversible write operation that creates new content on a card. It has minimal blast radius—a misused comment is easily deleted and causes no permanent harm or data loss. Unlike destructive operations (archive, close, delete), comments can be removed. Unlike financial operations, there is no monetary impact. Severity is low because comment spam or injected comments are trivial to remediate.
From the tool's definition Tool name 'add_comment' and description explicitly states 'Add a comment to a card' with purpose to 'add notes or feedback'. This is a create operation that adds new data to an existing card without modifying or deleting existing content.
Documented attack patterns abuse exactly the kind of access add_comment 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_comment:
{
"version": "1",
"default": "deny",
"tools": {
"add_comment": {
"limits": [
{
"counter": "add_comment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_comment 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 comment to a card. Use this tool to add notes or feedback to a card. 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_comment: 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_comment 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_comment 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_comment. 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_comment 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.