# rubber-duck MCP Server

Bridge to multiple LLMs and CLI agents: councils, debates, voting, and more

**Publisher claimed.** No tool list reported, and Pod has not connected to this server.

## Status

Pod has not dialled rubber-duck yet, so everything on this page is what its publisher reported rather than what we observed. Registries describe servers; they do not connect to them. Until a check runs, treat the tool list below as a claim.

## Connect

Published as `mcp-rubber-duck` on npm. Runs locally.

## Known issues

**52 problems reported by people outside the maintainer team.** Issues filed by the project's own owners, members and collaborators are excluded — those are release checklists and internal refactors, not things that will go wrong for you. Showing 12.

### Most discussed

### duck_debate 'Failed to retrieve task' error + suggestions for filesystem access and fire-and-forget wrapper

# Bug: duck_debate intermittently fails with "Failed to retrieve task: Task not found"

## Description

`duck_debate` intermittently fails with `MCP error -32602: Failed to retrieve task: Task not found`. This occurs randomly — not related to prompt size or provider selection. When it fails, ALL subsequent tool calls (compare_ducks, ask_duck, etc.) also fail for ~50s (the MCP client's 3-retry cycle).

## Root Cause (traced through source)

`duck_debate` is the only tool using `registerToolTask()

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/127) · 2026-07-19 · closed · external user · 4 comments

### 🚀 Migrate to Bun Runtime

# 🚀 Migrate to Bun Runtime

## Summary

Migrate MCP Rubber Duck from Node.js/npm to Bun as the primary runtime for faster builds, tests, and development experience.

**Approach:** Hybrid migration - Bun for runtime/build/test, Node.js for npm publish (due to [missing provenance support](https://github.com/oven-sh/bun/issues/15601) and [auth bugs in CI](https://github.com/oven-sh/bun/issues/24124)).

## Motivation

- **Speed**: Bun installs packages 20-40x faster than npm
- **Native TypeScript**:

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/41) · 2026-01-24 · open · 3 comments

### feat: Duck Autopilot - Automatic task decomposition & workflows

## 🦆 Duck Enhancement Proposal

```
     __
   <(o )___
    ( ._> /   "Quack! Just tell me your goal, I'll handle the rest!"
     `---'
```

### 💡 The Problem
**What problem would this feature solve?**

Complex tasks currently require manual orchestration:
- Users must decompose tasks into steps themselves
- Manual selection of which duck/tool to use for each step
- No automatic error recovery or replanning
- Can't leverage the full power of multi-duck + MCP tools together

### 🚀 Proposed Soluti

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/12) · 2026-01-08 · open · 3 comments

### feat: Streamable HTTP transport support

## 🦆 Duck Enhancement Proposal

### 💡 The Problem
The server currently only supports stdio transport, limiting deployment to local processes launched by MCP clients. This prevents:
- Remote/cloud deployment
- Horizontal scaling
- Web-based access
- Future Server Cards support (requires HTTP)

### 🚀 Proposed Solution
Add Streamable HTTP transport alongside existing stdio transport.

**Benefits:**
- Deploy as a standalone HTTP service
- Support multiple concurrent clients
- Enable cloud/container 

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/57) · 2026-02-05 · open · 2 comments

### feat: Add human-readable title to all tools

## 🦆 Duck Enhancement Proposal

### 💡 The Problem
Tools only have `name` and `description` fields. The MCP spec now supports a `title` field for human-readable display names, which improves UI presentation in clients.

### 🚀 Proposed Solution
Add `title` field to all tool definitions for better UX in MCP clients.

**Example:**
```typescript
this.server.tool('duck_council', {
  title: 'Duck Council',
  description: 'Convene multiple ducks to discuss a topic and reach consensus',
  // ...
})
```

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/54) · 2026-02-05 · closed · 2 comments

### Most recent

### duck_council: add a synthesis-only output mode (return the final report, not every duck's response)

Motivated by the "fire-and-forget wrapper" suggestion in #127.

`duck_council` currently returns **every duck's full verbose response**. When an agent offloads a whole council workflow, all of that lands in the caller's context.

### Ask
Add a **synthesis-only** output mode (or a verbosity flag) to `duck_council` — return just the final synthesized report instead of each duck's full answer. Optionally a `mode: full | synthesis` param, defaulting to current behavior for back-compat.

### Why this

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/131) · 2026-07-21 · open · 1 comment

### Docs: read-only filesystem MCP Bridge recipe (+ trusted-tools-gates-calls-not-tools caveat)

Requested in #127: give ducks read-only file access (source, configs, PDFs) during code review without manual copy-paste.

This already works today via the MCP Bridge — no code change needed. Any third-party filesystem MCP server plugs in through the existing env vars:

```yaml
MCP_SERVER_FS_TYPE: stdio
MCP_SERVER_FS_COMMAND: npx
MCP_SERVER_FS_ARGS: -y,@modelcontextprotocol/server-filesystem,/path/to/allowed/dir
MCP_SERVER_FS_ENABLED: 'true'
MCP_TRUSTED_TOOLS_FS: '*'
```

### Ask
Add a documente

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/130) · 2026-07-21 · closed · 1 comment

### MCP Bridge: global MCP_TRUSTED_TOOLS='*' ignored + server-name derivation can force approval prompts

Surfaced while investigating #127 (fixed in v1.20.1). The `MCP_APPROVAL_MODE=trusted` + `MCP_TRUSTED_TOOLS_*='*'` bypass works for the common **per-server** case, but two real edge cases can still force an approval prompt. `MCP_APPROVAL_MODE=never` is a working workaround meanwhile.

### 1. Global `MCP_TRUSTED_TOOLS='*'` is silently ignored

- `src/config/config.ts` parses `MCP_TRUSTED_TOOLS='*'` into a literal `Set(['*'])`.
- But the global fallback branch in `src/services/function-bridge.ts` c

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/129) · 2026-07-21 · open · 1 comment

### feat: duck_check — cross-vendor GO/BLOCK/ASK-HUMAN action gate for agents

## 🦆 Duck Enhancement Proposal

```
     __
   <(o )___
    ( ._> /   "Quack! Before you run that migration... let me get a second opinion."
     `---'
```

### 💡 The Problem
**What problem would this feature solve?**

When a coding agent (Claude Code / Cursor / Codex) is about to take a **risky action** — apply a diff, run a DB migration, execute a shell command, delete files — there is no cheap, cross-vendor "second opinion gate" it can consult *before* executing.

A single-model self-check is

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/120) · 2026-06-09 · open · 1 comment

### feat: duck_judge Panel — debiased multi-provider judging (position-bias swap, judge panel, agreement confidence, outputSchema)

## 🦆 Duck Enhancement Proposal

```
     __
   <(o )___
    ( ._> /   "I'll judge fairly... unless you put yourself first in the list."
     `---'
```

### 💡 The Problem

`duck_judge` exists to settle which duck gave the best answer — but today it does so with a **single, position-biased, schema-less** judge. That's exactly the part of the pipeline most vulnerable to silent, systematic error:

1. **One judge, no bias cancellation.** The judge defaults to the *first available provider* (`src/tool

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/119) · 2026-06-09 · open · 0 comments

### feat: Server Card (/.well-known/mcp/server-card.json)

## Summary

Implement Server Card support per draft spec SEP-1649 for auto-discovery by clients and crawlers without establishing a connection.

Split from #100 (Registry publish is done).

## References

- #49
- [SEP-1649: Server Cards](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1649)

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/101) · 2026-04-03 · open · 0 comments

### feat: MCP Registry publish + Server Card

## Summary

Remaining items from #97 — Registry listing and Server Card support.

## Items

- [ ] **Publish to MCP Registry** — namespace `io.github.nesquikm/rubber-duck` is ready. Use `mcp-publisher` CLI to list in the [official registry](https://registry.modelcontextprotocol.io/).
- [ ] **Server Card** (`/.well-known/mcp/server-card.json`) — #49. Draft spec (SEP-1649) for auto-discovery by clients and crawlers without establishing a connection.

## References

- [MCP Registry](https://registry

[Read the thread](https://github.com/nesquikm/mcp-rubber-duck/issues/100) · 2026-04-03 · closed · 1 comment

[See all 23 reports Pod holds for rubber-duck](/mcp/rubber-duck/issues) — of 52 qualified upstream.

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