slack_read_channel_messages
Reads recent messages from a Slack channel or DM. Reads from the local IndexedDB cache — only messages that Slack Desktop has synced to disk are available (typically the last few hundred messages for active channels). channel_id must come from slack_list_channels.
This record as markdown: /tools/com-local-mcp-local-mcp/slack-read-channel-messages.md
What slack_read_channel_messages does on Local
AI agents call slack_read_channel_messages to retrieve information from Local without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
limit | integer | — | Max messages to return (default 50) |
channel_id | string | Yes | Channel ID from slack_list_channels |
Parameters from the server's own tool schema.
Why slack_read_channel_messages is rated Low
This tool purely retrieves cached message data from Slack without any capability to modify, delete, execute code, or trigger external operations. The read-only nature and reliance on local IndexedDB data (rather than live API calls) minimizes risk.
From the tool's definition Tool name contains 'read' and description states 'Reads recent messages from a Slack channel or DM' with no modification, deletion, or execution capability. Data source is local IndexedDB cache with no side effects.
Attacks that exploit this kind of access
The rule that runs slack_read_channel_messages 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 slack_read_channel_messages, this is the rule to start with:
slack_read_channel_messages is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Local, apply this rule, and every slack_read_channel_messages call is checked against it from then on.
Questions about slack_read_channel_messages
Reads recent messages from a Slack channel or DM. Reads from the local IndexedDB cache — only messages that Slack Desktop has synced to disk are available (typically the last few hundred messages for active channels). channel_id must come from slack_list_channels. It is categorised as a Read tool in the Local MCP Server, which means it retrieves data without modifying state.
slack_read_channel_messages accepts 2 parameters: limit, channel_id. Required: channel_id. The full parameter table on this page comes from the server's own tool schema.
Register the Local MCP server in PolicyLayer and add a rule for slack_read_channel_messages: 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.
slack_read_channel_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the slack_read_channel_messages 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 slack_read_channel_messages. 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.
slack_read_channel_messages 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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