Librivox

Audiobook

audiobook

Read-onlyIdempotent

Single audiobook by id.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`id`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
`books`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed13 schema fields changedSep 16, 2026

removedOutput schema / properties / authors

Removed value: -{
-  "description": "List of authors",
-  "items": {
-    "properties": {
-      "id": {
-        "description": "Author ID",
-        "type": "number"
-      },
-      "name": {
-        "description": "Author name",
-        "type": "string"
-      }
-    },
-    "type": "object"
-  },
-  "type": "array"
-}

addedOutput schema / properties / books

Added value: +{
+  "items": {
+    "properties": {
+      "authors": {
+        "items": {
+          "properties": {
+            "dob": {
+              "type": "string"
+            },
+            "dod": {
+              "type": "string"
+            },
+            "first_name": {
+              "type": "string"
+            },
+            "id": {
+              "type": "string"
+            },
+            "last_name": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "copyright_year": {
+        "type": "string"
+      },
+      "description": {
+        "type": "string"
+      },
+      "id": {
+        "type": "string"
+      },
+      "language": {
+        "type": "string"
+      },
+      "num_sections": {
+        "type": "string"
+      },
+      "title": {
+        "type": "string"
+      },
+      "totaltime": {
+        "type": "string"
+      },
+      "totaltimesecs": {
+        "type": "number"
+      },
+      "url_librivox": {
+        "type": "string"
+      },
+      "url_other": {
+        "type": "string"
+      },
+      "url_project": {
+        "type": "string"
+      },
+      "url_rss": {
+        "type": "string"
+      },
+      "url_text_source": {
+        "type": "string"
+      },
+      "url_zip_file": {
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "type": "array"
+}

removedOutput schema / properties / cover_url

Removed value: -{
-  "description": "Cover image URL",
-  "type": "string"
-}

removedOutput schema / properties / date_added

Removed value: -{
-  "description": "Date added to LibriVox",
-  "type": "string"
-}

removedOutput schema / properties / description

Removed value: -{
-  "description": "Audiobook description",
-  "type": "string"
-}

removedOutput schema / properties / id

Removed value: -{
-  "description": "Audiobook ID",
-  "type": "number"
-}

removedOutput schema / properties / language

Removed value: -{
-  "description": "Language of audiobook",
-  "type": "string"
-}

removedOutput schema / properties / narrators

Removed value: -{
-  "description": "List of narrators",
-  "items": {
-    "properties": {
-      "id": {
-        "description": "Narrator ID",
-        "type": "number"
-      },
-      "name": {
-        "description": "Narrator name",
-        "type": "string"
-      }
-    },
-    "type": "object"
-  },
-  "type": "array"
-}

removedOutput schema / properties / project_gutenberg_id

Removed value: -{
-  "description": "Project Gutenberg ID if available",
-  "type": [
-    "number",
-    "null"
-  ]
-}

removedOutput schema / properties / title

Removed value: -{
-  "description": "Audiobook title",
-  "type": "string"
-}

removedOutput schema / properties / totaltime

Removed value: -{
-  "description": "Total duration in seconds",
-  "type": "number"
-}

removedOutput schema / properties / url_iarchive

Removed value: -{
-  "description": "Internet Archive URL",
-  "type": "string"
-}

removedOutput schema / properties / url_librivox

Removed value: -{
-  "description": "LibriVox page URL",
-  "type": "string"
-}

Changed2 schema fields changedMay 22, 2026

addedInput schema / examples

Added value: +[
+  {
+    "id": 1234
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "authors": {
+      "description": "List of authors",
+      "items": {
+        "properties": {
+          "id": {
+            "description": "Author ID",
+            "type": "number"
+          },
+          "name": {
+            "description": "Author name",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "cover_url": {
+      "description": "Cover image URL",
+      "type": "string"
+    },
+    "date_added": {
+      "description": "Date added to LibriVox",
+      "type": "string"
+    },
+    "description": {
+      "description": "Audiobook description",
+      "type": "string"
+    },
+    "id": {
+      "description": "Audiobook ID",
+      "type": "number"
+    },
+    "language": {
+      "description": "Language of audiobook",
+      "type": "string"
+    },
+    "narrators": {
+      "description": "List of narrators",
+      "items": {
+        "properties": {
+          "id": {
+            "description": "Narrator ID",
+            "type": "number"
+          },
+          "name": {
+            "description": "Narrator name",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "project_gutenberg_id": {
+      "description": "Project Gutenberg ID if available",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "title": {
+      "description": "Audiobook title",
+      "type": "string"
+    },
+    "totaltime": {
+      "description": "Total duration in seconds",
+      "type": "number"
+    },
+    "url_iarchive": {
+      "description": "Internet Archive URL",
+      "type": "string"
+    },
+    "url_librivox": {
+      "description": "LibriVox page URL",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedMay 18, 2026

TDQS

B3.3/5.0

Behavior3/5

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

Annotations already declare read-only, idempotent, and non-destructive behavior, so the safety profile is covered. The description adds the cardinality signal 'single' and the id-based selection behavior, but it does not disclose handling of missing/invalid ids or other runtime details.

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 words, front-loaded, no filler. Every word earns its place by identifying the resource, the cardinality, and the selection key.

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?

For a simple one-parameter lookup, the description is minimally invokable, and the output schema plus annotations cover safety and return shape. It still lacks explicit guidance on where the id comes from or when to choose this tool over the sibling 'audiobooks', so it is not fully complete.

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

Parameters2/5

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

Schema description coverage is 0%, so the description needed to carry parameter meaning. 'By id' merely restates the parameter name and does not explain the id's source, format, or valid values; the one parameter is self-explanatory, but the description adds little semantic value 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 is a noun phrase rather than an explicit verb, but it clearly identifies a single audiobook resource selected by id. The word 'single' distinguishes it from the plural sibling 'audiobooks', even though the description does not mention that sibling.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'by id' implies this is a point lookup for one specific audiobook, and the contrast with sibling 'audiobooks' suggests when to use it. However, there is no explicit statement of when to prefer it over alternatives or when not to use it.

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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