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

data_session_open

Buy per-query access to live data listings - first taste free via data_preview. Listing: RiverWatch: USGS river levels & stream-flow gauges (0.01 USDC/query (max 20 queries/session)). Open a prepaid session, then fund and query.

Input Schema

TableJSON Schema

Name	Required	Description
`listing_id`	No	UUID of the listing. Provide exactly one of listing_slug or listing_id.
`max_queries`	No
`listing_slug`	No	Public listing slug (from benchmarks_get / data_directory_get). Provide exactly one of listing_slug or listing_id.
`open_tx_hash`	No
`buyer_address`	No	Buyer EVM address. Optional: defaults to your own platform wallet when omitted.
`proof_escrow_id`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed13 schema fields changedSep 7, 2026

addedInput schema / description

Added value: +"MCP-only input for ``data_session_open``.\n\nSubclasses the REST ``DataSessionOpen`` payload without mutating it (the\n``FaucetUsdcDripInput`` approach) so the shared constraints\n(``max_queries`` bounds, ``open_tx_hash`` length, the EVM address check)\nstay declared once. Two friction-free relaxations, MCP surface only:\n\n* the listing may be named by its public slug OR its UUID (exactly one) -\n  the benchmark route and the purchase-gate 409 hand the agent a slug, and\n  demanding a UUID re-creates the slug-to-UUID lookup hop;\n* ``buyer_address`` is optional - when omitted the handler defaults to the\n  caller's own platform wallet (``WalletService.own_wallet_address``),\n  the same argument-filling default the USDC faucet uses.\n\nThe REST endpoint ``POST /api/v1/data-sessions`` keeps requiring\n``listing_id`` + ``buyer_address`` unchanged.\n\nThe ``type: ignore[assignment]`` marks are the intended pydantic override\n(narrowing the REST fields to Optional here); mypy reads that as an LSP\nviolation even though the model validator enforces exactly one listing\nreference and the handler guards the Optionals."

addedInput schema / properties / buyer_address / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / buyer_address / default
```
Added value: +null
```

addedInput schema / properties / buyer_address / description

Added value: +"Buyer EVM address. Optional: defaults to your own platform wallet when omitted."

removedInput schema / properties / buyer_address / type
```
Removed value: -"string"
```

addedInput schema / properties / listing_id / anyOf

Added value: +[
+  {
+    "format": "uuid",
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / listing_id / default
```
Added value: +null
```

addedInput schema / properties / listing_id / description

Added value: +"UUID of the listing. Provide exactly one of listing_slug or listing_id."

removedInput schema / properties / listing_id / format
```
Removed value: -"uuid"
```
removedInput schema / properties / listing_id / type
```
Removed value: -"string"
```

addedInput schema / properties / listing_slug

Added value: +{
+  "anyOf": [
+    {
+      "minLength": 1,
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Public listing slug (from benchmarks_get / data_directory_get). Provide exactly one of listing_slug or listing_id.",
+  "title": "Listing Slug"
+}

removedInput schema / required

Removed value: -[
-  "listing_id",
-  "buyer_address"
-]

changedInput schema / title

Previous value: -"DataSessionOpen"New value: +"DataSessionOpenInput"

First observedSep 6, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations only indicate not read-only and not idempotent; the description adds meaningful behavior: it creates a prepaid session, defaults all optional parameters, enforces max queries, and explains that the REST endpoint still requires listing_id and buyer_address. The description does not fully disclose failure modes or postconditions, but it adds context beyond annotations.

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

Conciseness4/5

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

The tool description is concise and front-loaded with the core action and cost/limit. The schema description is long and includes implementation details (pydantic override, type ignore marks) that an agent doesn't need. That drags the score down slightly; the tool-level description itself earns a 5 but the overall package includes technical noise.

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

Completeness4/5

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

Despite having 6 params, no required params, no output schema, and payment-sensitive behavior, the description plus schema explanations give the agent enough to call the tool: what to pass, cost, free alternative, session/query limits. Missing output/return expectations and explicit next-step guidance (e.g., then call data_session_fund) are minor gaps.

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

Parameters5/5

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

Schema description coverage is 50%, but the description and schema description compensate heavily: listing_slug and listing_id are explicitly required exactly-one, buyer_address is optional with wallet-service default, max_queries has bounds shown in schema, open_tx_hash and proof_escrow_id are contextual but the schema's descriptions plus the tool narrative provide enough semantics. The description goes beyond the schema by explaining why slug is allowed and how defaults work.

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

Purpose5/5

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

The description clearly states the action (buy per-query access), the resource (live data listings), and the flow (open a prepaid session). It names the listing (RiverWatch: USGS river levels) and pricing/model (prepaid, max 20 queries/session), and it contrasts with data_preview as a free first taste. This differentiates it from sibling tools like data_session_fund and data_session_query.

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

Usage Guidelines4/5

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

The description explicitly says to use data_preview for a free first taste, which gives an alternative. The schema describes slug-vs-id usage and payment defaults. But it doesn't explicitly state when not to use this tool or compare against data_session_fund / data_session_attach_escrow / data_session_query. The context is clear but exclusions are missing.

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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