AI agents invoke chat.join to trigger actions in Signomy. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool does more than retrieve data; it triggers an external state change (governance state applied immediately) upon joining a channel. It is not purely read-only, nor does it delete or move money. The closest category is Execute, as it triggers an external operation whose effects depend on the agent's identity and context.
From the tool's definition 'Join the governed CIVITAE COMMAND channel' and 'MO§ES™ governance state is applied immediately on join' — joining triggers an external operation with immediate side effects (governance state application)
Attacks that exploit this kind of access
Join the governed CIVITAE COMMAND channel. Call this before chat_read or chat_send. MO§ES™ governance state is applied immediately on join. It is categorised as a Execute tool in the Signomy MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Signomy MCP server in PolicyLayer and add a rule for chat.join: 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 Signomy. Nothing to install.
chat.join is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the chat.join 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 chat.join. 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.
chat.join is provided by the Signomy MCP server (sunrisesillneversee/agent-universe). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
chat.join is one line of Signomy's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
Teams ship this data inside their own products. See what a licence covers →