AI agents use line_send_flex_message to create or update resources in UnClick — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your UnClick environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
to | string | Yes | |
alt_text | string | Yes | Fallback text shown in push notifications |
contents | object | Yes | Flex Message container as JSON object or string |
channel_access_token | string | Yes |
Parameters from the server's own tool schema.
This tool sends messages to LINE users or groups, which is a reversible write operation. It creates new data (messages) but does not delete, execute arbitrary code, or involve financial transactions. The severity is medium because an agent could spam users or send unwanted messages, but the impact is limited to message creation without access to sensitive data or destructive capabilities.
From the tool's definition Tool name 'line_send_flex_message' and description 'Send a rich Flex Message to a LINE user or group' indicate the tool creates/sends a message, which is a write operation that modifies state (adds a message to a conversation).
Attacks that exploit this kind of access
Send a rich Flex Message to a LINE user or group. It is categorised as a Write tool in the UnClick MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
line_send_flex_message accepts 4 parameters: to, alt_text, contents, channel_access_token. Required: to, alt_text, contents, channel_access_token. The full parameter table on this page comes from the server's own tool schema.
Register the UnClick MCP server in PolicyLayer and add a rule for line_send_flex_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 UnClick. Nothing to install.
line_send_flex_message 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 line_send_flex_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.
Set action: deny in the PolicyLayer policy for line_send_flex_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.
line_send_flex_message is provided by the UnClick MCP server (@unclick/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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