Sends an event to a Data Source in Tinybird. The data needs to be in NDJSON format and conform to the Data Source schema in Tinybird
AI agents use save-event to create or update resources in Tinybird MCP server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Tinybird MCP server environment.
This tool creates new records in a Tinybird Data Source by appending events. While it modifies state, it is reversible (events can be deleted or data sources reset), so it does not rise to Destructive. It does not execute arbitrary code or trigger external operations beyond the write itself, so Execute does not apply.
From the tool's definition Tool description states it 'Sends an event to a Data Source in Tinybird' and requires data in NDJSON format conforming to a schema. The verb 'Sends' and the action of populating a data source constitute data creation/modification.
Documented attack patterns abuse exactly the kind of access save-event gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Tinybird MCP server, and nothing reaches the server without passing your rules. This is the rule we recommend for save-event:
{
"version": "1",
"default": "deny",
"tools": {
"save-event": {
"limits": [
{
"counter": "save-event_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}save-event 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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Sends an event to a Data Source in Tinybird. The data needs to be in NDJSON format and conform to the Data Source schema in Tinybird. It is categorised as a Write tool in the Tinybird MCP server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Tinybird MCP server MCP server in PolicyLayer and add a rule for save-event: 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 Tinybird MCP server. Nothing to install.
save-event 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 save-event 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 save-event. 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.
save-event is provided by the Tinybird MCP server MCP server (tinybirdco/mcp-tinybird). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 11 Tinybird MCP server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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11 Tinybird MCP server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.