Npi Registry

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Read-onlyIdempotent

Search providers by any combination of fields. NPI Registry requires at least one filter — supply at least name/organization/taxonomy/postal_code/state.

Input Schema

Name	Required	Description
`city`	No
`name`	No	Full provider name (use along with type)
`skip`	No	0-based offset (max 1000)
`limit`	No	1-200 (default 10)
`state`	No	Two-letter state code
`number`	No	10-digit NPI
`npi_type`	No	NPI-1 (individual) \| NPI-2 (organization)
`taxonomy`	No	Taxonomy code or description (e.g. "Internal Medicine")
`last_name`	No
`first_name`	No
`postal_code`	No	5-digit ZIP (or first 3 with wildcard "*")
`country_code`	No	US (default) \| other ISO country
`address_purpose`	No	LOCATION (default) \| MAILING \| PRIMARY \| SECONDARY
`organization_name`	No

Output Schema

Name	Required	Description
`Errors`	No	API error messages if any
`results`	No	Array of provider records matching search criteria
`result_count`	No	Total number of results matching query

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedMay 24, 2026

addedInput schema / examples

Added value: +[
+  {
+    "name": "John Smith",
+    "state": "CA",
+    "taxonomy": "Internal Medicine"
+  },
+  {
+    "limit": 20,
+    "organization_name": "Mayo Clinic",
+    "state": "MN"
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "Errors": {
+      "description": "API error messages if any",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "result_count": {
+      "description": "Total number of results matching query",
+      "type": "number"
+    },
+    "results": {
+      "description": "Array of provider records matching search criteria",
+      "items": {
+        "properties": {
+          "addresses": {
+            "description": "Provider address records",
+            "items": {
+              "properties": {
+                "address_1": {
+                  "type": "string"
+                },
+                "address_2": {
+                  "type": "string"
+                },
+                "address_purpose": {
+                  "type": "string"
+                },
+                "address_type": {
+                  "type": "string"
+                },
+                "city": {
+                  "type": "string"
+                },
+                "country_code": {
+                  "type": "string"
+                },
+                "postal_code": {
+                  "type": "string"
+                },
+                "state": {
+                  "type": "string"
+                }
+              },
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "basic": {
+            "description": "Basic provider information",
+            "properties": {
+              "credential_text": {
+                "type": "string"
+              },
+              "first_name": {
+                "type": "string"
+              },
+              "last_name": {
+                "type": "string"
+              },
+              "organization_name": {
+                "type": "string"
+              }
+            },
+            "type": "object"
+          },
+          "enumeration_type": {
+            "description": "NPI-1 (individual) or NPI-2 (organization)",
+            "type": "string"
+          },
+          "number": {
+            "description": "10-digit NPI identifier",
+            "type": "string"
+          },
+          "taxonomies": {
+            "description": "Provider taxonomy specializations",
+            "items": {
+              "properties": {
+                "code": {
+                  "type": "string"
+                },
+                "primary": {
+                  "type": "boolean"
+                },
+                "taxonomy_description": {
+                  "type": "string"
+                }
+              },
+              "type": "object"
+            },
+            "type": "array"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

First observedMay 13, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already indicate read-only, open-world, idempotent, and non-destructive behavior, so the description's additional note about filter requirements adds useful context without contradicting annotations. The tool's safety profile is effectively communicated.

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?

The description is two sentences: the first states the general purpose, the second adds a critical usage constraint. No wasted words, front-loaded with key information.

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?

Given the high schema coverage, existence of an output schema, and annotations, the description is adequately complete. It covers the essential constraint. Minor improvement could be adding why the filter requirement exists, but not necessary.

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?

With 71% schema description coverage, the schema documents most parameters well. The description adds no new parameter information beyond listing suggested filter fields, which is already implicit in the schema. Baseline 3 is appropriate.

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 tool searches for providers using any combination of fields. It specifies the resource ('providers') and the action ('search'), distinguishing it from sibling tools like 'get_provider' which likely retrieves a single record.

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 provides clear context that the NPI Registry requires at least one filter, listing acceptable fields. While it does not explicitly mention when not to use this tool or name alternatives, the requirement gives practical usage guidance.

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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