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usgs-water-mcp-server

by io.github.cyanheads
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Water Dataframe Describe

water_dataframe_describe
Read-onlyIdempotent

List tables and columns staged on a DataCanvas by water_get_series or water_find_sites. Call this after water_get_series or water_find_sites returns a canvas_id to discover the exact table name and column types before writing a query. Then pass the table name to water_dataframe_query, or to water_dataframe_drop (when this server enables it) to remove a table you no longer need. Requires DataCanvas to be enabled on this server instance. Returns an error if DataCanvas is not available.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
canvas_idYesCanvas ID returned by water_get_series or water_find_sites. Identifies the canvas to describe.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
errorNoPresent when the call failed. Absent on success.
tablesNoTables and views on this canvas.
canvas_idNoThe canvas ID that was described — pass to water_dataframe_query.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedInput schema / properties / canvas_id / pattern
      Added value: +"^[A-Za-z0-9_-]{10}$"
  2. Changed6 schema fields changed
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • addedInput schema / additionalProperties
      Added value: +false
    • changedOutput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
    • addedOutput schema / anyOf
      Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "tables",
+      "canvas_id"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]
    • addedOutput schema / properties / error
      Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `canvas_disabled`: DataCanvas is not enabled on this server instance. `canvas_not_found`: The canvas_id does not exist or has expired. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "canvas_disabled",
+            "canvas_not_found"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}
    • removedOutput schema / required
      Removed value: -[
-  "tables",
-  "canvas_id"
-]
  3. Changed1 schema field changed
    • changedInput schema / properties / canvas_id / description
      Previous value: -"Canvas ID returned by water_get_series. Identifies the canvas to describe."New value: +"Canvas ID returned by water_get_series or water_find_sites. Identifies the canvas to describe."
  4. First observed

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuine environmental context beyond that: DataCanvas must be enabled on the server instance, an error is returned if it is not, and drop is only available 'when this server enables it'. This conditional-capability disclosure is valuable and not in the annotations.

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

Conciseness5/5

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

Front-loaded with purpose, then sequencing, then next-step routing, then the environmental requirement. Four tight sentences, each carrying distinct information with no redundancy.

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

Completeness5/5

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

An output schema exists, so return values need no explanation, and annotations cover the safety profile. The description still supplies prerequisites, workflow routing, and the DataCanvas-enabled error condition, making it complete for an agent to call this correctly.

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 the single canvas_id parameter is documented in the schema with its origin and purpose. The description adds no syntax, format, or constraint detail beyond what the schema already provides, so the baseline 3 applies.

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 states a specific verb and resource ('List tables and columns staged on a DataCanvas') and explicitly ties the resource to the tools that create it (water_get_series, water_find_sites). An agent can distinguish it from water_dataframe_query (querying) and water_dataframe_drop (removing) without opening any schema.

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

Usage Guidelines5/5

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

It gives explicit when-to-use ('Call this after water_get_series or water_find_sites returns a canvas_id to discover the exact table name and column types before writing a query') and names the specific follow-on tools (water_dataframe_query, water_dataframe_drop). Prerequisite and sequencing are fully spelled out.

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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