musicbrainz-mcp-server

musicbrainz-mcp-server: lookup identifier

musicbrainz_lookup_identifier

Read-onlyIdempotent

Resolve a standard identifier to MusicBrainz entities without a name search — the deterministic path when you already hold an ID. id_type=isrc → recordings (a recording-level code, often shared by several recordings); id_type=iswc → works (a composition-level code); id_type=barcode → releases (UPC/EAN digits; spaces and hyphens are ignored). ISRC and ISWC hit dedicated exact endpoints; barcode is a Lucene search filter so results are ranked (exact match scores 100). The output kind field tells you which entity type came back.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`value`	Yes	The identifier value. ISRC e.g. "USRC17607839"; ISWC e.g. "T-010.140.236-1"; barcode = the UPC/EAN digits, e.g. "075678164125" (spaces and hyphens are ignored; any other character, including a wildcard, is rejected).
`id_type`	Yes	Which standard identifier: isrc (recording), iswc (work), or barcode (release).

Output Schema

TableJSON Schema

Name	Required	Description	Default
`error`	No	Present when the call failed. Absent on success.
`result`	No	The resolved entities, discriminated by `kind` (recordings \| works \| releases).

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 22, 2026

changedInput schema / properties / value / description

Previous value: -"The identifier value. ISRC e.g. \"USRC17607839\"; ISWC e.g. \"T-010.140.236-1\"; barcode e.g. \"075678164125\"."New value: +"The identifier value. ISRC e.g. \"USRC17607839\"; ISWC e.g. \"T-010.140.236-1\"; barcode = the UPC/EAN digits, e.g. \"075678164125\" (spaces and hyphens are ignored; any other character, including a wildcard, is rejected)."

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `identifier_not_found`: The identifier is well-formed but resolves to zero entities. `invalid_identifier`: The ISRC/ISWC is malformed (the dedicated endpoint returns HTTP 400). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `identifier_not_found`: The identifier is well-formed but resolves to zero entities. `invalid_identifier`: The ISRC/ISWC is malformed (the dedicated endpoint returns HTTP 400), or the barcode contains anything other than digits once spaces and hyphens are removed. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / result / oneOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "ISRC result arm: recordings carrying the ISRC.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "recordings",
-        "description": "ISRC resolved to recordings.",
-        "type": "string"
-      },
-      "recordings": {
-        "description": "Recordings carrying this ISRC.",
-        "items": {
-          "additionalProperties": false,
-          "description": "A recording carrying the looked-up ISRC.",
-          "properties": {
-            "artistCredit": {
-              "description": "Credited artist string; falls back to \"Unknown artist\" when none is recorded.",
-              "type": "string"
-            },
-            "length": {
-              "description": "Recording length as m:ss. Omitted when unknown.",
-              "type": "string"
-            },
-            "mbid": {
-              "description": "Recording MBID — chain to musicbrainz_get_recording.",
-              "type": "string"
-            },
-            "title": {
-              "description": "Recording title.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title",
-            "artistCredit"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "recordings"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "ISWC result arm: works carrying the ISWC.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "works",
-        "description": "ISWC resolved to works.",
-        "type": "string"
-      },
-      "works": {
-        "description": "Works carrying this ISWC.",
-        "items": {
-          "additionalProperties": false,
-          "description": "A work carrying the looked-up ISWC.",
-          "properties": {
-            "mbid": {
-              "description": "Work MBID — chain to musicbrainz_get_work.",
-              "type": "string"
-            },
-            "title": {
-              "description": "Work title.",
-              "type": "string"
-            },
-            "type": {
-              "description": "Work type. Omitted when absent.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "works"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Barcode result arm: releases carrying the barcode.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "releases",
-        "description": "Barcode resolved to releases.",
-        "type": "string"
-      },
-      "releases": {
-        "description": "Releases carrying this barcode (ranked).",
-        "items": {
-          "additionalProperties": false,
-          "description": "A release carrying the looked-up barcode.",
-          "properties": {
-            "artistCredit": {
-              "description": "Credited artist string.",
-              "type": "string"
-            },
-            "country": {
-              "description": "Release country code. Omitted when absent.",
-              "type": "string"
-            },
-            "date": {
-              "description": "Release date. Omitted when absent.",
-              "type": "string"
-            },
-            "mbid": {
-              "description": "Release MBID — chain to musicbrainz_get_release.",
-              "type": "string"
-            },
-            "score": {
-              "description": "Lucene relevance score, 0–100 (barcode is a search filter; exact = 100).",
-              "type": "number"
-            },
-            "title": {
-              "description": "Release title.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title",
-            "artistCredit",
-            "score"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "releases"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "ISRC result arm: recordings carrying the ISRC.",
+    "properties": {
+      "identifier": {
+        "description": "The looked-up identifier value.",
+        "type": "string"
+      },
+      "kind": {
+        "const": "recordings",
+        "description": "ISRC resolved to recordings.",
+        "type": "string"
+      },
+      "recordings": {
+        "description": "Recordings carrying this ISRC.",
+        "items": {
+          "additionalProperties": false,
+          "description": "A recording carrying the looked-up ISRC.",
+          "properties": {
+            "artistCredit": {
+              "description": "Credited artist string; falls back to \"Unknown artist\" when none is recorded.",
+              "type": "string"
+            },
+            "length": {
+              "description": "Recording length as m:ss. Omitted when unknown.",
+              "type": "string"
+            },
+            "mbid": {
+              "description": "Recording MBID — chain to musicbrainz_get_recording.",
+              "type": "string"
+            },
+            "title": {
+              "description": "Recording title.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title",
+            "artistCredit"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "recordings"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "ISWC result arm: works carrying the ISWC.",
+    "properties": {
+      "identifier": {
+        "description": "The looked-up identifier value.",
+        "type": "string"
+      },
+      "kind": {
+        "const": "works",
+        "description": "ISWC resolved to works.",
+        "type": "string"
+      },
+      "works": {
+        "description": "Works carrying this ISWC.",
+        "items": {
+          "additionalProperties": false,
+          "description": "A work carrying the looked-up ISWC.",
+          "properties": {
+            "mbid": {
+              "description": "Work MBID — chain to musicbrainz_get_work.",
+              "type": "string"
+            },
+            "title": {
+              "description": "Work title.",
+              "type": "string"
+            },
+            "type": {
+              "description": "Work type. Omitted when absent.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "works"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Barcode result arm: releases carrying the barcode.",
+    "properties": {
+      "identifier": {
+        "description": "The barcode digits that were searched (spaces and hyphens removed).",
+        "type": "string"
+      },
+      "kind": {
+        "const": "releases",
+        "description": "Barcode resolved to releases.",
+        "type": "string"
+      },
+      "releases": {
+        "description": "Releases carrying this barcode (ranked).",
+        "items": {
+          "additionalProperties": false,
+          "description": "A release carrying the looked-up barcode.",
+          "properties": {
+            "artistCredit": {
+              "description": "Credited artist string.",
+              "type": "string"
+            },
+            "country": {
+              "description": "Release country code. Omitted when absent.",
+              "type": "string"
+            },
+            "date": {
+              "description": "Release date. Omitted when absent.",
+              "type": "string"
+            },
+            "mbid": {
+              "description": "Release MBID — chain to musicbrainz_get_release.",
+              "type": "string"
+            },
+            "score": {
+              "description": "Lucene relevance score, 0–100 (barcode is a search filter; exact = 100).",
+              "type": "number"
+            },
+            "title": {
+              "description": "Release title.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title",
+            "artistCredit",
+            "score"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "releases"
+    ],
+    "type": "object"
+  }
+]

Changed6 schema fields changedAug 21, 2026

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": [
+      "result"
+    ]
+  },
+  {
+    "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: `identifier_not_found`: The identifier is well-formed but resolves to zero entities. `invalid_identifier`: The ISRC/ISWC is malformed (the dedicated endpoint returns HTTP 400). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "identifier_not_found",
+            "invalid_identifier"
+          ],
+          "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: -[
-  "result"
-]
```

Changed2 schema fields changedJun 20, 2026

changedInput schema / properties / value / description

Previous value: -"The identifier value. ISRC e.g. \"USRC17607839\"; ISWC e.g. \"T-345246800-1\"; barcode e.g. \"075678164125\"."New value: +"The identifier value. ISRC e.g. \"USRC17607839\"; ISWC e.g. \"T-010.140.236-1\"; barcode e.g. \"075678164125\"."

changedOutput schema / properties / result / oneOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "description": "ISRC result arm: recordings carrying the ISRC.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "recordings",
-        "description": "ISRC resolved to recordings.",
-        "type": "string"
-      },
-      "recordings": {
-        "description": "Recordings carrying this ISRC.",
-        "items": {
-          "additionalProperties": false,
-          "description": "A recording carrying the looked-up ISRC.",
-          "properties": {
-            "artistCredit": {
-              "description": "Credited artist string.",
-              "type": "string"
-            },
-            "length": {
-              "description": "Recording length as m:ss. Omitted when unknown.",
-              "type": "string"
-            },
-            "mbid": {
-              "description": "Recording MBID — chain to musicbrainz_get_recording.",
-              "type": "string"
-            },
-            "title": {
-              "description": "Recording title.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title",
-            "artistCredit"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "recordings"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "ISWC result arm: works carrying the ISWC.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "works",
-        "description": "ISWC resolved to works.",
-        "type": "string"
-      },
-      "works": {
-        "description": "Works carrying this ISWC.",
-        "items": {
-          "additionalProperties": false,
-          "description": "A work carrying the looked-up ISWC.",
-          "properties": {
-            "mbid": {
-              "description": "Work MBID — chain to musicbrainz_get_work.",
-              "type": "string"
-            },
-            "title": {
-              "description": "Work title.",
-              "type": "string"
-            },
-            "type": {
-              "description": "Work type. Omitted when absent.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "works"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "description": "Barcode result arm: releases carrying the barcode.",
-    "properties": {
-      "identifier": {
-        "description": "The looked-up identifier value.",
-        "type": "string"
-      },
-      "kind": {
-        "const": "releases",
-        "description": "Barcode resolved to releases.",
-        "type": "string"
-      },
-      "releases": {
-        "description": "Releases carrying this barcode (ranked).",
-        "items": {
-          "additionalProperties": false,
-          "description": "A release carrying the looked-up barcode.",
-          "properties": {
-            "artistCredit": {
-              "description": "Credited artist string.",
-              "type": "string"
-            },
-            "country": {
-              "description": "Release country code. Omitted when absent.",
-              "type": "string"
-            },
-            "date": {
-              "description": "Release date. Omitted when absent.",
-              "type": "string"
-            },
-            "mbid": {
-              "description": "Release MBID — chain to musicbrainz_get_release.",
-              "type": "string"
-            },
-            "score": {
-              "description": "Lucene relevance score, 0–100 (barcode is a search filter; exact = 100).",
-              "type": "number"
-            },
-            "title": {
-              "description": "Release title.",
-              "type": "string"
-            }
-          },
-          "required": [
-            "mbid",
-            "title",
-            "artistCredit",
-            "score"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      }
-    },
-    "required": [
-      "kind",
-      "identifier",
-      "releases"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "description": "ISRC result arm: recordings carrying the ISRC.",
+    "properties": {
+      "identifier": {
+        "description": "The looked-up identifier value.",
+        "type": "string"
+      },
+      "kind": {
+        "const": "recordings",
+        "description": "ISRC resolved to recordings.",
+        "type": "string"
+      },
+      "recordings": {
+        "description": "Recordings carrying this ISRC.",
+        "items": {
+          "additionalProperties": false,
+          "description": "A recording carrying the looked-up ISRC.",
+          "properties": {
+            "artistCredit": {
+              "description": "Credited artist string; falls back to \"Unknown artist\" when none is recorded.",
+              "type": "string"
+            },
+            "length": {
+              "description": "Recording length as m:ss. Omitted when unknown.",
+              "type": "string"
+            },
+            "mbid": {
+              "description": "Recording MBID — chain to musicbrainz_get_recording.",
+              "type": "string"
+            },
+            "title": {
+              "description": "Recording title.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title",
+            "artistCredit"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "recordings"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "ISWC result arm: works carrying the ISWC.",
+    "properties": {
+      "identifier": {
+        "description": "The looked-up identifier value.",
+        "type": "string"
+      },
+      "kind": {
+        "const": "works",
+        "description": "ISWC resolved to works.",
+        "type": "string"
+      },
+      "works": {
+        "description": "Works carrying this ISWC.",
+        "items": {
+          "additionalProperties": false,
+          "description": "A work carrying the looked-up ISWC.",
+          "properties": {
+            "mbid": {
+              "description": "Work MBID — chain to musicbrainz_get_work.",
+              "type": "string"
+            },
+            "title": {
+              "description": "Work title.",
+              "type": "string"
+            },
+            "type": {
+              "description": "Work type. Omitted when absent.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "works"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "description": "Barcode result arm: releases carrying the barcode.",
+    "properties": {
+      "identifier": {
+        "description": "The looked-up identifier value.",
+        "type": "string"
+      },
+      "kind": {
+        "const": "releases",
+        "description": "Barcode resolved to releases.",
+        "type": "string"
+      },
+      "releases": {
+        "description": "Releases carrying this barcode (ranked).",
+        "items": {
+          "additionalProperties": false,
+          "description": "A release carrying the looked-up barcode.",
+          "properties": {
+            "artistCredit": {
+              "description": "Credited artist string.",
+              "type": "string"
+            },
+            "country": {
+              "description": "Release country code. Omitted when absent.",
+              "type": "string"
+            },
+            "date": {
+              "description": "Release date. Omitted when absent.",
+              "type": "string"
+            },
+            "mbid": {
+              "description": "Release MBID — chain to musicbrainz_get_release.",
+              "type": "string"
+            },
+            "score": {
+              "description": "Lucene relevance score, 0–100 (barcode is a search filter; exact = 100).",
+              "type": "number"
+            },
+            "title": {
+              "description": "Release title.",
+              "type": "string"
+            }
+          },
+          "required": [
+            "mbid",
+            "title",
+            "artistCredit",
+            "score"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "required": [
+      "kind",
+      "identifier",
+      "releases"
+    ],
+    "type": "object"
+  }
+]

First observedJun 16, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already mark it read-only and idempotent, and the description adds key behavioral context: ISRC/ISWC hit dedicated exact endpoints, while barcode is a Lucene search filter with ranked results and exact matches scoring 100. It also tells agents to expect a kind field identifying the returned entity type. No contradictions.

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?

Four dense sentences, all load-bearing, with the core decision first and mode-specific nuances following. It avoids repeating the schema and contains no filler.

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?

For a read-only lookup with a full input schema and an output schema, the description covers the workflow decision, endpoint behavior differences, and output shape signal. Nothing an agent needs to correctly invoke or interpret the tool is missing.

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

Parameters5/5

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

The schema already documents both parameters completely, and the description enriches them by explaining what each identifier type represents, that ISRC can map to multiple recordings, and that barcode results are ranked with exact matches at 100. This is genuine added meaning beyond the schema.

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?

Opens with a specific verb-resource pair ('Resolve a standard identifier to MusicBrainz entities') and immediately contrasts it with name search, establishing this as the deterministic ID-based lookup. It maps each id_type to its entity class, which clearly distinguishes it from the musicbrainz_search_entities and musicbrainz_get_* siblings.

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?

Explicitly frames the tool as the deterministic path when an ID is already held, and says 'without a name search', which sets a clear boundary against search_entities. The id_type mapping also tells agents which entity type each mode returns. It does not name sibling tools directly, but the guidance is sufficient.

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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