Copies a file into the managed attachments folder for a Trellis issue. Errors if the issue does not exist, the source file does not exist, or a file with the same name already exists in the attachments folder.
AI agents use add_attachment to create or update resources in Task Trellis MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Task Trellis MCP environment.
The tool creates a new attachment by copying a file into a managed folder. This is a reversible write operation (the attachment can be deleted via other tools like delete_issue). It does not execute arbitrary code, move money, or permanently destroy data. The medium severity reflects that an agent could spam attachments or attach malicious files, but the blast radius is limited to a single issue's attachments folder.
From the tool's definition Tool description states it 'Copies a file into the managed attachments folder for a Trellis issue', which is a create/modify operation that adds data to the system.
Documented attack patterns abuse exactly the kind of access add_attachment gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Task Trellis MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for add_attachment:
{
"version": "1",
"default": "deny",
"tools": {
"add_attachment": {
"limits": [
{
"counter": "add_attachment_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_attachment 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.
Copies a file into the managed attachments folder for a Trellis issue. Errors if the issue does not exist, the source file does not exist, or a file with the same name already exists in the attachments folder. It is categorised as a Write tool in the Task Trellis MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Task Trellis MCP server in PolicyLayer and add a rule for add_attachment: 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 Task Trellis MCP. Nothing to install.
add_attachment 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_attachment 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_attachment. 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_attachment is provided by the Task Trellis MCP server (langadventurellc/task-trellis-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Task Trellis MCP, 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.
16 Task Trellis MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.