add_chat_message_attachment
Attach a file directly to a Huly channel message, direct-message message, or thread reply. Provide filename, contentType, and exactly one source: ${UPLOAD_SOURCE_SEMANTICS}
This record as markdown: /tools/io-github-dearlordylord-huly-mcp/add-chat-message-attachment.md
What add_chat_message_attachment does on Huly
AI agents use add_chat_message_attachment to create or update resources in Huly, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Huly environment.
Why add_chat_message_attachment is rated Medium
This tool creates or modifies data by attaching files to messages—a reversible write operation. It does not delete data (not Destructive), execute arbitrary code (not Execute), move money (not Financial), or merely read (not Read).
From the tool's definition Tool description states 'Attach a file directly to a Huly channel message, direct-message message, or thread reply' which creates new attachment data associated with existing messages.
Attacks that exploit this kind of access
The rule that runs add_chat_message_attachment safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Huly, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For add_chat_message_attachment, this is the rule to start with:
add_chat_message_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.
The button opens the PolicyLayer dashboard: create your workspace, connect Huly, apply this rule, and every add_chat_message_attachment call is checked against it from then on.
Questions about add_chat_message_attachment
Attach a file directly to a Huly channel message, direct-message message, or thread reply. Provide filename, contentType, and exactly one source: ${UPLOAD_SOURCE_SEMANTICS}. It is categorised as a Write tool in the Huly MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Huly MCP server in PolicyLayer and add a rule for add_chat_message_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 Huly. Nothing to install.
add_chat_message_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_chat_message_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_chat_message_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_chat_message_attachment is provided by the Huly MCP server (@firfi/huly-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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