Calculer une zone accessible depuis un point en un temps donné (isochrone) ou une distance donnée (isodistance)
AI agents invoke calculate_isochrone to trigger actions in French Open Data & IGN. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool performs a geographic computation (isochrone/isodistance calculation) that triggers an external routing/geospatial operation based on input parameters. While it returns data, it executes a non-trivial computation against an external service rather than simply retrieving stored data. No data is written or destroyed, and there are no financial implications.
From the tool's definition Calculer une zone accessible depuis un point en un temps donné (isochrone) ou une distance donnée (isodistance)
Documented attack patterns abuse exactly the kind of access calculate_isochrone gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and French Open Data & IGN, and nothing reaches the server without passing your rules. This is the rule we recommend for calculate_isochrone:
{
"version": "1",
"default": "deny",
"tools": {
"calculate_isochrone": {
"limits": [
{
"counter": "calculate_isochrone_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}calculate_isochrone stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Calculer une zone accessible depuis un point en un temps donné (isochrone) ou une distance donnée (isodistance). It is categorised as a Execute tool in the French Open Data & IGN MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the French Open Data & IGN MCP server in PolicyLayer and add a rule for calculate_isochrone: 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 French Open Data & IGN. Nothing to install.
calculate_isochrone is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the calculate_isochrone 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 calculate_isochrone. 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.
calculate_isochrone is provided by the French Open Data & IGN MCP server (nikoko107/mcp-datagouv-ign). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from French Open Data & IGN, 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.
26 French Open Data & IGN tools catalogued and risk-classified — across an index of 43,000+ MCP servers.