AI agents use update_snippet to create or update resources in PhonePi MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your PhonePi MCP environment.
This tool modifies existing data (snippets) on a mobile device but does not execute code, delete data irreversibly, move money, or access sensitive information. The modification is reversible (snippets can be re-edited or restored), making it a Write-category action. Severity is low because snippets are typically small text fragments with limited blast radius if misused.
From the tool's definition Tool name is 'update_snippet' and description states 'Update an existing snippet', which is a reversible modification operation.
Documented attack patterns abuse exactly the kind of access update_snippet gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PhonePi MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for update_snippet:
{
"version": "1",
"default": "deny",
"tools": {
"update_snippet": {
"limits": [
{
"counter": "update_snippet_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_snippet 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 an existing snippet. It is categorised as a Write tool in the PhonePi MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the PhonePi MCP server in PolicyLayer and add a rule for update_snippet: 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 PhonePi MCP. Nothing to install.
update_snippet 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_snippet 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_snippet. 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_snippet is provided by the PhonePi MCP server (priyankark/phonepi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 22 PhonePi MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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22 PhonePi MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.