gutenberg-mcp-server

Browse Popular Gutenberg Books

gutenberg_browse_popular

Read-onlyIdempotent

Browse the most-downloaded Project Gutenberg books, ordered by popularity. Returns up to 32 titles with their Gutenberg IDs, authors, languages, and download counts. Optionally filter by language or topic. Use this as a discovery entry point — "what are the most popular classics in French?" — or as a heartbeat check that the catalog is reachable.

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Number of books to return (1–32). Default 20 gives a useful overview without overwhelming context.
`topic`	No	Filter by a subject or bookshelf keyword (case-insensitive phrase match). Example: "science fiction", "adventure", "detective". Applies on top of the language filter.
`languages`	No	Restrict to books in these languages (two-character ISO 639-1 codes). Example: ["en"] for English only, ["de", "fr"] for German or French. Omit for all languages.

Output Schema

TableJSON Schema

Name	Required	Description
`cap`	No	The limit that was applied.
`books`	No	Top books by download count, most popular first.
`error`	No	Present when the call failed. Absent on success.
`shown`	No	Number of books returned in this response.
`truncated`	No	True when the catalog held more matches than were returned.
`totalInCatalog`	No	Total books matching the filter in the full catalog (useful for context — "top 20 of 60,000").
`truncationCeiling`	No	Download count of the least-popular book shown — omitted books have at most this many downloads.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedSep 20, 2026
- removedOutput schema / properties / books / items / properties / authors / items / properties / birth_year / anyOf
```
Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / books / items / properties / authors / items / properties / birth_year / type
```
Added value: +[
+  "number",
+  "null"
+]
```
- removedOutput schema / properties / books / items / properties / authors / items / properties / death_year / anyOf
```
Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / books / items / properties / authors / items / properties / death_year / type
```
Added value: +[
+  "number",
+  "null"
+]
```

Changed2 schema fields changedAug 23, 2026

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

Previous value: -"Machine-readable failure mode. Declared by this tool: `no_results`: No books match the language/topic filter combination. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `no_results`: No books match the language/topic filter combination. `catalog_unavailable`: The Project Gutenberg catalog did not answer within the time this server allows for one browse. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / error / properties / data / properties / reason / examples

Previous value: -[
-  "no_results"
-]New value: +[
+  "no_results",
+  "catalog_unavailable"
+]

Changed6 schema fields changedAug 22, 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": [
+      "books",
+      "totalInCatalog",
+      "truncated",
+      "shown",
+      "cap"
+    ]
+  },
+  {
+    "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: `no_results`: No books match the language/topic filter combination. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "no_results"
+          ],
+          "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: -[
-  "books",
-  "totalInCatalog",
-  "truncated",
-  "shown",
-  "cap"
-]

Changed1 schema field changedJul 11, 2026

changedOutput schema / properties / books / items / properties / has_plain_text / description

Previous value: -"True if media_type is \"Text\" AND a text/plain format is available via gutenberg_get_text."New value: +"True if media_type is \"Text\" AND a UTF-8 text/plain format is available via gutenberg_get_text."

First observedJun 16, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare the tool read-only, idempotent, and open-world. The description adds useful behavioral context: it returns up to 32 titles with Gutenberg IDs, authors, languages, and download counts, and that filtering is optional. It does not disclose much beyond this, but the annotations cover the main safety profile.

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?

Two front-loaded sentences deliver the action, result scope, ordering, filters, and canonical use cases with no repetition or filler. Every sentence earns its place.

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 read-only tool with no required parameters and an output schema, this description gives enough information to select and call it correctly. It could be slightly stronger by explicitly naming gutenberg_search_books for targeted queries, but the discovery framing already separates it from siblings.

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?

Schema coverage is 100%, with detailed per-parameter descriptions including defaults, examples, and match semantics. The free-text description only says 'Optionally filter by language or topic,' so it does not materially add meaning beyond what the schema already provides.

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 opens with a specific verb and resource: browse the most-downloaded Project Gutenberg books, ordered by popularity. It names the returned fields and frames the tool as a discovery entry point, clearly distinguishing it from the sibling search/get tools.

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 explicitly positions this as a discovery entry point and a heartbeat check, with an example question like 'what are the most popular classics in French?'. It does not explicitly name sibling alternatives or state when not to use it, so it lacks full exclusion 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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