nwis.streamflow.annual_stats
Get year-by-year annual mean streamflow statistics for a USGS gauge station. Returns mean discharge (ft3/s) for each water year with records going back to 1900s at major stations. Useful for long-term hydrologic trend analysis, climate change assessment, and water resource planning. Typical major...
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What nwis.streamflow.annual_stats does on Apibase
AI agents call nwis.streamflow.annual_stats to retrieve information from Apibase without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
site_no | string | Yes | USGS gauge station number, 8–15 digits (e.g. "01646500" for Potomac River near DC). Use water.sites to find station numbers. |
Parameters from the server's own tool schema.
Why nwis.streamflow.annual_stats is rated Low
Tool retrieves historical hydrologic data without modification, deletion, or external effects.
From the tool's definition Get year-by-year annual mean streamflow statistics. Returns mean discharge. Public domain, unlimited calls.
Attacks that exploit this kind of access
The rule that runs nwis.streamflow.annual_stats safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Apibase, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For nwis.streamflow.annual_stats, this is the rule to start with:
nwis.streamflow.annual_stats is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Apibase, apply this rule, and every nwis.streamflow.annual_stats call is checked against it from then on.
Questions about nwis.streamflow.annual_stats
Get year-by-year annual mean streamflow statistics for a USGS gauge station. Returns mean discharge (ft3/s) for each water year with records going back to 1900s at major stations. Useful for long-term hydrologic trend analysis, climate change assessment, and water resource planning. Typical major stations have 60–90 years of annual records. Use water.sites to look up station numbers by state or bounding box. No auth — USGS public domain, unlimited calls. It is categorised as a Read tool in the Apibase MCP Server, which means it retrieves data without modifying state.
nwis.streamflow.annual_stats accepts 1 parameter: site_no. Required: site_no. The full parameter table on this page comes from the server's own tool schema.
Register the Apibase MCP server in PolicyLayer and add a rule for nwis.streamflow.annual_stats: 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 Apibase. Nothing to install.
nwis.streamflow.annual_stats is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the nwis.streamflow.annual_stats 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 nwis.streamflow.annual_stats. 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.
nwis.streamflow.annual_stats is provided by the Apibase MCP server (apibase-mcp-client). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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