Read canvas content using canvases.sections.lookup. Pass Slack params in
AI agents call read_canvas to retrieve information from Slack Max API MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves canvas content from Slack without creating, modifying, or deleting any data. It is a query operation that has no side effects on the Slack workspace. The low severity reflects the minimal risk of misuse — reading canvas content cannot damage data or cause unintended consequences beyond information disclosure.
From the tool's definition Tool name is 'read_canvas' and description states 'Read canvas content using canvases.sections.lookup'. The verb 'read' and 'lookup' indicate data retrieval with no modification or side effects.
Attacks that exploit this kind of access
Read canvas content using canvases.sections.lookup. Pass Slack params in. It is categorised as a Read tool in the Slack Max API MCP MCP Server, which means it retrieves data without modifying state.
Register the Slack Max API MCP server in PolicyLayer and add a rule for read_canvas: 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 Slack Max API MCP. Nothing to install.
read_canvas 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 read_canvas 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 read_canvas. 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.
read_canvas is provided by the Slack Max API MCP server (jeongwoobin335/slack-mcp). 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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