mcp-rubber-duck

Compare Ducks

compare_ducks

Read-only

Send a prompt to multiple language models simultaneously to gather diverse answers and compare responses.

Instructions

Ask the same question to multiple ducks simultaneously

Input Schema

TableJSON Schema

Name	Required	Description
`model`	No	Specific model to use for all providers (optional)
`images`	No	Optional images to include with the prompt (for vision-capable models)
`prompt`	Yes	The question to ask all ducks
`providers`	No	List of provider names to query (optional, uses all if not specified)

Output Schema

TableJSON Schema

Name	Required	Description	Default
`responses`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Addedv1.19.6May 15, 2026
Removedv1.19.5May 11, 2026

Changed5 schema fields changedv1.2.3May 2, 2026

addedInput schema / $schema

Added value: +"http://json-schema.org/draft-07/schema#"

addedInput schema / additionalProperties
```
Added value: +false
```

addedInput schema / properties / images

Added value: +{
+  "description": "Optional images to include with the prompt (for vision-capable models)",
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "data": {
+        "description": "Base64-encoded image data",
+        "type": "string"
+      },
+      "mimeType": {
+        "description": "MIME type (e.g., \"image/png\") — required for base64 data, optional for URLs",
+        "type": "string"
+      },
+      "url": {
+        "description": "Image URL — passed directly to the LLM provider",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "type": "array"
+}

addedInput schema / properties / providers / items / enum

Added value: +[
+  "openai",
+  "google",
+  "groq",
+  "ollama"
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "responses": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "content": {
+            "type": "string"
+          },
+          "error": {
+            "type": "string"
+          },
+          "latency": {
+            "type": "number"
+          },
+          "model": {
+            "type": "string"
+          },
+          "nickname": {
+            "type": "string"
+          },
+          "provider": {
+            "type": "string"
+          },
+          "tokens": {
+            "anyOf": [
+              {
+                "additionalProperties": false,
+                "properties": {
+                  "completion": {
+                    "type": "number"
+                  },
+                  "prompt": {
+                    "type": "number"
+                  },
+                  "total": {
+                    "type": "number"
+                  }
+                },
+                "required": [
+                  "prompt",
+                  "completion",
+                  "total"
+                ],
+                "type": "object"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          }
+        },
+        "required": [
+          "provider",
+          "nickname",
+          "model",
+          "content",
+          "latency",
+          "tokens"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "responses"
+  ],
+  "type": "object"
+}

First observedv1.0.0Jan 5, 2026

TDQS

A3.8/5.0

Behavior3/5

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

Annotations already indicate readOnlyHint=true (safe read) and openWorldHint=true, so the description adds no extra behavioral context beyond aligning with those traits. No contradiction.

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?

The description is a single, front-loaded sentence with no waste, perfectly efficient for the tool's purpose.

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?

Given good annotations and full schema coverage, the description covers essential aspects. However, it omits details about the response format or how results from multiple ducks are presented, which could be useful.

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 full descriptions for all 4 parameters; the description adds no 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 clearly states the verb 'ask' and resource 'multiple ducks simultaneously', which distinguishes it from siblings like ask_duck (single duck) and duck_debate (debate format).

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 description implies usage for parallel queries but does not explicitly state when to use versus alternatives like duck_debate or duck_council, nor provides when-not-to-use 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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