Update the content of an existing document in the knowledge base. Mutating — overwrites the file on disk and re-indexes immediately. Old chunks are removed and replaced with new ones. Full content replacement, not a patch. Args: filepath: Full or relative path to the document file. Must be an alr...
AI agents use update_document to create or update resources in Knowledge Rag — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Knowledge Rag environment.
This tool creates or modifies data reversibly by replacing document content and updating the index. While it overwrites existing data, the operation is reversible (a new update_document call could restore previous content, or a backup could be recovered). This is Write-category behavior rather than Destructive because the intent is modification, not irreversible deletion.
From the tool's definition Tool description states: 'Mutating — overwrites the file on disk and re-indexes immediately. Old chunks are removed and replaced with new ones.
Documented attack patterns abuse exactly the kind of access update_document gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Knowledge Rag, and nothing reaches the server without passing your rules. This is the rule we recommend for update_document:
{
"version": "1",
"default": "deny",
"tools": {
"update_document": {
"limits": [
{
"counter": "update_document_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_document 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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Update the content of an existing document in the knowledge base. Mutating — overwrites the file on disk and re-indexes immediately. Old chunks are removed and replaced with new ones. Full content replacement, not a patch. Args: filepath: Full or relative path to the document file. Must be an already-indexed file — use list_documents() to find valid paths. content: New full-text content to replace the existing content entirely Returns: JSON string with update results (old chunk count, new chunk count, status). Usage: Use to replace a document's content completely. Use add_document() to create a new file instead. Use remove_document() to delete without replacing. Changes are immediately searchable — no manual reindex needed. It is categorised as a Write tool in the Knowledge Rag MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Knowledge Rag MCP server in PolicyLayer and add a rule for update_document: 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 Knowledge Rag. Nothing to install.
update_document 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 update_document 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 update_document. 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.
update_document is provided by the Knowledge Rag MCP server (lyonzin/knowledge-rag). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Knowledge Rag, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
12 Knowledge Rag tools catalogued and risk-classified — across an index of 43,000+ MCP servers.