Opentargets

Target Known Drugs

target_known_drugs

Read-onlyIdempotent

"What drugs target [gene]" / "approved drugs against [target]" / "clinical-trial drugs for [gene]" — drugs that have been clinically tested or approved against a drug target (Ensembl gene ID). Returns drug names, mechanisms, indications, clinical trial phases. Use for competitive landscape / drug-repositioning queries.

Input Schema

Name	Required	Description	Default
`size`	No	1-100 (default 25)
`ensembl_id`	Yes

Output Schema

Name	Required	Description	Default
`target`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 11, 2026

removedOutput schema / properties / data

Removed value: -{
-  "properties": {
-    "target": {
-      "properties": {
-        "approvedSymbol": {
-          "description": "Target symbol",
-          "type": "string"
-        },
-        "id": {
-          "description": "Target ID",
-          "type": "string"
-        },
-        "knownDrugs": {
-          "properties": {
-            "count": {
-              "description": "Total known drugs",
-              "type": "integer"
-            },
-            "rows": {
-              "items": {
-                "properties": {
-                  "disease": {
-                    "properties": {
-                      "name": {
-                        "description": "Disease name",
-                        "type": "string"
-                      }
-                    },
-                    "type": "object"
-                  },
-                  "drug": {
-                    "properties": {
-                      "maximumClinicalTrialPhase": {
-                        "description": "Max trial phase",
-                        "type": "integer"
-                      },
-                      "name": {
-                        "description": "Drug name",
-                        "type": "string"
-                      }
-                    },
-                    "type": "object"
-                  },
-                  "drugId": {
-                    "description": "Drug ID",
-                    "type": "string"
-                  },
-                  "phase": {
-                    "description": "Clinical trial phase",
-                    "type": "integer"
-                  }
-                },
-                "type": "object"
-              },
-              "type": "array"
-            }
-          },
-          "type": "object"
-        }
-      },
-      "type": "object"
-    }
-  },
-  "type": "object"
-}

addedOutput schema / properties / target

Added value: +{
+  "properties": {
+    "approvedSymbol": {
+      "type": "string"
+    },
+    "drugAndClinicalCandidates": {
+      "properties": {
+        "count": {
+          "type": "number"
+        },
+        "rows": {
+          "items": {
+            "properties": {
+              "diseases": {
+                "items": {
+                  "properties": {
+                    "disease": {
+                      "properties": {
+                        "id": {
+                          "type": "string"
+                        },
+                        "name": {
+                          "type": "string"
+                        }
+                      },
+                      "type": [
+                        "null",
+                        "object"
+                      ]
+                    },
+                    "diseaseFromSource": {
+                      "type": "string"
+                    }
+                  },
+                  "type": "object"
+                },
+                "type": "array"
+              },
+              "drug": {
+                "properties": {
+                  "drugType": {
+                    "type": "string"
+                  },
+                  "id": {
+                    "type": "string"
+                  },
+                  "name": {
+                    "type": "string"
+                  }
+                },
+                "type": "object"
+              },
+              "id": {
+                "type": "string"
+              },
+              "maxClinicalStage": {
+                "type": "string"
+              }
+            },
+            "type": "object"
+          },
+          "type": "array"
+        }
+      },
+      "type": "object"
+    },
+    "id": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed2 schema fields changedMay 22, 2026

addedInput schema / examples

Added value: +[
+  {
+    "ensembl_id": "ENSG00000141510"
+  },
+  {
+    "ensembl_id": "ENSG00000141510",
+    "size": 50
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "data": {
+      "properties": {
+        "target": {
+          "properties": {
+            "approvedSymbol": {
+              "description": "Target symbol",
+              "type": "string"
+            },
+            "id": {
+              "description": "Target ID",
+              "type": "string"
+            },
+            "knownDrugs": {
+              "properties": {
+                "count": {
+                  "description": "Total known drugs",
+                  "type": "integer"
+                },
+                "rows": {
+                  "items": {
+                    "properties": {
+                      "disease": {
+                        "properties": {
+                          "name": {
+                            "description": "Disease name",
+                            "type": "string"
+                          }
+                        },
+                        "type": "object"
+                      },
+                      "drug": {
+                        "properties": {
+                          "maximumClinicalTrialPhase": {
+                            "description": "Max trial phase",
+                            "type": "integer"
+                          },
+                          "name": {
+                            "description": "Drug name",
+                            "type": "string"
+                          }
+                        },
+                        "type": "object"
+                      },
+                      "drugId": {
+                        "description": "Drug ID",
+                        "type": "string"
+                      },
+                      "phase": {
+                        "description": "Clinical trial phase",
+                        "type": "integer"
+                      }
+                    },
+                    "type": "object"
+                  },
+                  "type": "array"
+                }
+              },
+              "type": "object"
+            }
+          },
+          "type": "object"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "type": "object"
+}

First observedMay 14, 2026

TDQS

A4.1/5.0

Behavior3/5

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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is fully covered. The description adds the data domain (clinical trial phases, mechanisms), but since an output schema exists, this overlaps structured data and adds little novel behavioral context beyond 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.

Conciseness4/5

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

Front-loads example queries, then a precise definition, then return contents, then use case. Every clause is relevant and it avoids waste, though the description packs several distinct pieces into one dense block.

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?

For a simple two-parameter lookup, the description covers purpose, target identifier format, returned fields, and use context; annotations cover safety and an output schema covers returns. Little is missing, though naming the nearest sibling alternatives would make selection fully unambiguous.

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

Parameters4/5

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

Schema coverage is 50%, with ensembl_id having no schema description; the description compensates by clarifying it is an "Ensembl gene ID," which is real value beyond the schema. The size parameter is already documented in the schema as "1-100 (default 25)," so the description need not cover it.

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?

States a specific verb+resource: drugs clinically tested or approved against a drug target identified by Ensembl gene ID. The quoted example queries ("What drugs target [gene]") and the Ensembl ID scoping distinguish it cleanly from siblings like target_associations and drug.

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?

"Use for competitive landscape / drug-repositioning queries" gives clear context for when to reach for this tool. It does not name the alternative sibling tools (e.g., target_associations, drug) or state when-not to use it, so it falls short of the explicit routing a 5 requires.

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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