Rxnorm

Rxnorm Related

rxnorm_related

Read-onlyIdempotent

Find related medications by RxCUI — brands, generics, ingredients, and dose forms. Maps between brand and generic alternatives. Use to compare drug options.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`tty`	No	Optional term type filter: BN (brand name), IN (ingredient), SBD (semantic branded drug), SCD (semantic clinical drug), GPCK (generic pack), BPCK (branded pack); other RxNorm term types such as PIN, MIN, DF and DFG also work. For several, separate them with a comma, a plus or a space — "BN,SBD", "BN+SBD" and "BN SBD" are all accepted and equivalent. Case does not matter. Omit for the default set (IN, BN, SBD, SCD, GPCK, BPCK).
`rxcui`	Yes	RxNorm concept ID, or a drug name (e.g. "aspirin") — resolved to an RxCUI automatically.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`rxcui`	Yes	RxNorm concept unique identifier
`related_groups`	Yes	Groups of related drug concepts by term type

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 3, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "rxcui": "7052"
-  },
-  {
-    "rxcui": "1243465",
-    "tty": "BN,SBD"
-  }
-]New value: +[
+  {
+    "rxcui": "7052"
+  },
+  {
+    "rxcui": "83367",
+    "tty": "BN,SBD"
+  },
+  {
+    "rxcui": "83367",
+    "tty": "BN+SBD"
+  }
+]

changedInput schema / properties / tty / description

Previous value: -"Optional term type filter: BN (brand name), IN (ingredient), SBD (semantic branded drug), SCD (semantic clinical drug), GPCK (generic pack), BPCK (branded pack). Comma-separated for multiple."New value: +"Optional term type filter: BN (brand name), IN (ingredient), SBD (semantic branded drug), SCD (semantic clinical drug), GPCK (generic pack), BPCK (branded pack); other RxNorm term types such as PIN, MIN, DF and DFG also work. For several, separate them with a comma, a plus or a space — \"BN,SBD\", \"BN+SBD\" and \"BN SBD\" are all accepted and equivalent. Case does not matter. Omit for the default set (IN, BN, SBD, SCD, GPCK, BPCK)."

Changed1 schema field changedJul 13, 2026

changedInput schema / properties / rxcui / description

Previous value: -"RxNorm concept ID"New value: +"RxNorm concept ID, or a drug name (e.g. \"aspirin\") — resolved to an RxCUI automatically."

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "related_groups": {
+      "description": "Groups of related drug concepts by term type",
+      "items": {
+        "properties": {
+          "concepts": {
+            "description": "Related drug concepts",
+            "items": {
+              "properties": {
+                "name": {
+                  "description": "Drug name",
+                  "type": "string"
+                },
+                "rxcui": {
+                  "description": "RxNorm concept unique identifier",
+                  "type": "string"
+                },
+                "tty": {
+                  "description": "Term type code",
+                  "type": "string"
+                }
+              },
+              "required": [
+                "rxcui",
+                "name",
+                "tty"
+              ],
+              "type": "object"
+            },
+            "type": "array"
+          },
+          "term_type": {
+            "description": "RxNorm term type filter applied",
+            "type": "string"
+          }
+        },
+        "required": [
+          "term_type",
+          "concepts"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "rxcui": {
+      "description": "RxNorm concept unique identifier",
+      "type": "string"
+    }
+  },
+  "required": [
+    "rxcui",
+    "related_groups"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "rxcui": "7052"
+  },
+  {
+    "rxcui": "1243465",
+    "tty": "BN,SBD"
+  }
+]

First observedApr 22, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations already establish the operation as read-only, idempotent, open-world, and non-destructive, so the description only needs to add behavioral context. It explains what the tool returns—related medications across brand, generic, ingredient, and dose-form categories—and describes the brand/generic mapping behavior. No contradiction with annotations exists.

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 description is compact and front-loads the core behavior, with only a short usage directive at the end. The final sentence is somewhat generic, but it does not add meaningful waste, so the structure remains efficient.

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?

The description is sufficient for a read-oriented relationship lookup tool when combined with a fully covered input schema, rich annotations, and an output schema. It conveys the relationship categories and intended use while leaving parameter formatting details to the schema, which already handles them thoroughly.

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?

Input schema coverage is 100%, and the schema already documents rxcui (including drug-name resolution) and the tty filter with accepted values, separators, case-insensitivity, and defaults. The description's reference to brands, generics, ingredients, and dose forms aligns with tty values but adds no parameter details beyond the schema.

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 states a specific action ('Find related medications by RxCUI') and enumerates the relationship categories returned: brands, generics, ingredients, and dose forms. It is clear and scoped, but it does not explicitly differentiate itself from sibling tools like rxnorm_search or rxnorm_get_properties.

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 a direct use case: 'Use to compare drug options,' and the mapping sentence supports the brand-to-generic alternative scenario. It does not state when not to use the tool or mention a preferred alternative, so it stops short of full usage guidance.

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

All Rxnorm tools Inspect

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