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ArcGIS Pro MCP

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get_unique_values

Retrieve distinct values for a field with row counts. Use to explore attribute data or apply a where clause and limit in ArcGIS Pro.

Instructions

Distinct values of a field with the count of rows for each.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fieldYesField name.
limitNoMaximum distinct values to return.
whereNoSQL where clause.
map_nameNoMap to act on; defaults to the active map.
layer_nameYesLayer or table name as shown by get_layers, or a full dataset path.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed6 schema fields changedv1.1.1
    • addedInput schema / properties / field / description
      Added value: +"Field name."
    • addedInput schema / properties / layer_name / description
      Added value: +"Layer or table name as shown by get_layers, or a full dataset path."
    • changedInput schema / properties / limit / default
      Previous value: -100New value: +200
    • addedInput schema / properties / limit / description
      Added value: +"Maximum distinct values to return."
    • addedInput schema / properties / map_name / description
      Added value: +"Map to act on; defaults to the active map."
    • addedInput schema / properties / where
      Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "SQL where clause.",
+  "title": "Where"
+}
  2. First observedv0.1.0

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden, and it discloses only the output shape (values plus counts). It does not state that this is a read-only operation, whether the limit/default interact, or anything about cost on large layers.

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?

A single tight sentence that front-loads the core output. It is efficient, though it reads as a noun fragment rather than a complete statement of what the tool does for the caller.

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?

An output schema exists, so return values need not be explained, and all parameters are covered by the schema. What is missing is the minimal orientation an agent needs for a 5-parameter query tool: that it is read-only and how the filter and limit scope the result.

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%, so all five parameters (field, layer_name, limit, where, map_name) are already documented in the schema. The description adds nothing about how where or limit affect the distinct-value computation, so the baseline of 3 applies.

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

Purpose4/5

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

The description names a specific operation and resource: distinct values of a field, plus the per-value row count. That is enough to know what the tool returns, but it never distinguishes itself from overlapping siblings such as get_field_statistics, summarize_features, or list_fields, which an agent could easily pick instead.

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?

There is no when-to-use guidance and no mention of alternatives, despite several sibling tools producing overlapping field-level summaries. The agent is left to infer that this is the right choice for categorical value counts.

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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