Add a member to a card. Use this tool to assign someone to a card.
AI agents use add_member 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 a new association (member assignment) on a card, which is a reversible modification of data. It does not execute code, delete data irreversibly, or involve financial transactions. The severity is medium because assigning incorrect members to cards could affect team workflows and task visibility, but the action is easily reversible by removing the member.
From the tool's definition Tool description states 'Add a member to a card' and 'assign someone to a card', indicating modification of card properties through addition of data.
Documented attack patterns abuse exactly the kind of access add_member 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_member:
{
"version": "1",
"default": "deny",
"tools": {
"add_member": {
"limits": [
{
"counter": "add_member_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_member 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 member to a card. Use this tool to assign someone 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_member: 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_member 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_member 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_member. 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_member 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.