AI agents use fold_block to create or update resources in SiYuan MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your SiYuan MCP Server environment.
Folding a block in a note-taking app is a UI/display state change that collapses a block visually. This is a reversible write operation (it can be unfolded), affecting display state rather than content. Severity is low as it only changes the visual presentation of a block.
From the tool's definition Tool name 'fold_block' and description '折叠块' (fold block)
Documented attack patterns abuse exactly the kind of access fold_block gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and SiYuan MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for fold_block:
{
"version": "1",
"default": "deny",
"tools": {
"fold_block": {
"limits": [
{
"counter": "fold_block_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}fold_block 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.
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折叠块. It is categorised as a Write tool in the SiYuan MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the SiYuan MCP Server MCP server in PolicyLayer and add a rule for fold_block: 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 SiYuan MCP Server. Nothing to install.
fold_block 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 fold_block 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 fold_block. 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.
fold_block is provided by the SiYuan MCP Server MCP server (xgq18237/siyuan_mcp_server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 52 SiYuan MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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52 SiYuan MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.