signal_send_message

SERVERLocal SOURCElocal-mcp

Medium RISK CLASS

Category Write

Parameters 32 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/com-local-mcp-local-mcp/signal-send-message.md

WHAT IT DOES

What signal_send_message does on Local

AI agents use signal_send_message to create or update resources in Local, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Local environment.

Parameter	Type	Required	Description
`text`	string	Yes	Plain-text message body
`chat_id`	string	Yes	Chat ID from signal_list_chats
`confirm`	boolean	—	Set true for send guidance. Default: preview only.

Parameters from the server's own tool schema.

RISK

Why signal_send_message is rated Medium

This tool enables creation and modification of messages destined for Signal chats. While the actual transmission occurs outside the MCP server (via Signal Desktop UI guidance), the tool's purpose is to facilitate sending messages, which is a Write operation. It creates new data (messages) in a reversible way—sent messages can be edited or deleted.

From the tool's definition Tool description states 'Preview (and get send guidance for) a message to a Signal chat' and 'Pass confirm=true to get step-by-step guidance for completing the send.' The tool facilitates message composition and transmission workflow, with the final send…

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs signal_send_message safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Local, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For signal_send_message, this is the rule to start with:

signal_send_message Rate-limited

signal_send_message 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "signal_send_message": {
      "limits": [
        {
          "counter": "signal_send_message_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Local, apply this rule, and every signal_send_message call is checked against it from then on.

FAQ

Questions about signal_send_message

What does the signal_send_message tool do? +

Preview (and get send guidance for) a message to a Signal chat. NOTE: Signal Desktop exposes no local send API — the Signal integration reads the local database read-only — so LMCP cannot transmit Signal messages directly. The first call (confirm=false or omitted) returns a preview. Pass confirm=true to get step-by-step guidance for completing the send. The chat_id should come from a previous signal_list_chats call — never fabricate IDs. It is categorised as a Write tool in the Local MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does signal_send_message accept? +

signal_send_message accepts 3 parameters: text, chat_id, confirm. Required: text, chat_id. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on signal_send_message? +

Register the Local MCP server in PolicyLayer and add a rule for signal_send_message: 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 Local. Nothing to install.

What risk level is signal_send_message? +

signal_send_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit signal_send_message? +

Yes. Add a rate_limit block to the signal_send_message 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.

How do I block signal_send_message completely? +

Set action: deny in the PolicyLayer policy for signal_send_message. 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.

What MCP server provides signal_send_message? +

signal_send_message is provided by the Local MCP server (local-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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