Generate a time series chart of air quality data. Returns a PNG chart image with a brief text summary. Use this when users ask about trends, patterns, or want to visualise air quality over time. Args: start_date: Start date (ISO format, e.g. "2025-01-01"). end_date: End date (ISO format). locatio...
Part of the Hermes — Air Quality Intelligence server.
Free to start. No card required.
AI agents invoke chart_aq_trend to trigger processes or run actions in Hermes — Air Quality Intelligence. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
chart_aq_trend can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. PolicyLayer enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
{
"version": "1",
"default": "deny",
"tools": {
"chart_aq_trend": {
"limits": [
{
"counter": "chart_aq_trend_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}See the full Hermes — Air Quality Intelligence policy for all 15 tools.
These attack patterns abuse exactly the kind of access chart_aq_trend gives an agent. Each links to the full case and the policy that stops it:
Other execute tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Generate a time series chart of air quality data. Returns a PNG chart image with a brief text summary. Use this when users ask about trends, patterns, or want to visualise air quality over time. Args: start_date: Start date (ISO format, e.g. "2025-01-01"). end_date: End date (ISO format). location: Postcode, place name, or "lat,lon". Provide this or site_code. site_code: Direct site code. Provide this or location. pollutants: Optional filter, e.g. ["NO2", "PM2.5"]. Defaults to NO2, PM2.5, PM10, O3 if not specified. frequency: "hourly", "daily", or "monthly" (default "daily"). show_who_guidelines: Show WHO guideline reference lines (default True). show_daqi_bands: Show DAQI band background shading (default True).. It is categorised as a Execute tool in the Hermes — Air Quality Intelligence MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Hermes — Air Quality Intelligence MCP server in PolicyLayer and add a rule for chart_aq_trend: 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 Hermes — Air Quality Intelligence. Nothing to install.
chart_aq_trend 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 chart_aq_trend 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 chart_aq_trend. 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.
chart_aq_trend is provided by the Hermes — Air Quality Intelligence MCP server (https://hermes.southlondonscientific.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 15 Hermes — Air Quality Intelligence tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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