RiverWatch: USGS river levels & stream-flow gauges — per query

data_preview

Read-onlyIdempotent

✅ No API key needed. Listing: RiverWatch: USGS river levels & stream-flow gauges. Price 0.01 USDC/query (max 20 queries/session). Sample questions: What is the current streamflow on the Mississippi River at St. Louis?; Which river gauges reported the highest levels in the last hour?. FREE preview — no key, no payment. Try one of the sample questions now.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "data_preview"
  }
}

Input Schema

Name	Required	Description	Default
`slug`	No	Public listing slug. Defaults to the routed session's listing when connected via /mcp/data/{slug}/http.
`question`	No	Optional free-text question you'd ask this data (echoed back).

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 6, 2026

TDQS

C2.8/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description does add useful operational context — no API key required, a per-session query cap of 20, and a stated price — which is genuine value beyond the annotations. However, the pricing line ("0.01 USDC/query") directly conflicts with the repeated claim that the preview is free, muddying rather than clarifying cost behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

It is short and front-loaded, but much of the text is promotional filler and redundancy: "No API key needed" is restated as "FREE preview — no key, no payment," and the closing call to action adds nothing operational. The checkmark emoji and marketing tone dilute an otherwise compact blurb.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-required-parameter, read-only preview with full schema coverage and no output schema, most of what an agent needs is present. What is missing is a clear statement of what the preview actually returns (metadata only) and a coherent cost model, since "free" and "0.01 USDC/query" appear side by side and could mislead an agent about whether calling it incurs charges.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and both parameters (`slug`, `question`) are documented in the schema, so the baseline of 3 applies. The sample questions illustrate how to phrase a `question` value, but the description adds no information about `slug` routing or what happens when it is omitted.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose3/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description identifies the underlying data ("RiverWatch: USGS river levels & stream-flow gauges") and calls this a "FREE preview," but it never states plainly that the tool returns a preview/metadata of a listing rather than the data itself — that framing only appears in the input schema's description. It also hard-codes one specific listing, so the agent cannot tell whether it previews that listing only or any listing via the `slug` parameter.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage guidance is limited to marketing calls to action ("Try one of the sample questions now") and sample queries. There is no statement of when to use this versus `data_session_open` or `data_session_query`, and no explicit exclusions or prerequisites beyond "no key needed."

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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