OpenCode Prompt Improver Plugin

An OpenCode plugin that automatically evaluates prompts for clarity and triggers research-based clarification when prompts are vague or ambiguous.

Based on claude-code-prompt-improver.

Installation

bun add @codymclain/opencode-prompt-improver

Or add to your OpenCode config:

{
  "plugins": ["@codymclain/opencode-prompt-improver"]
}

How It Works

The plugin intercepts user messages and evaluates them for clarity using pattern matching. When a prompt is determined to be vague (score < 60/100), it automatically injects context instructing the agent to:

1. Research Phase: Explore the codebase, check conversation history, find relevant files
2. Generate Clarifying Questions: Ask 1-4 targeted questions with options grounded in actual codebase findings
3. Wait for User Response: Don't proceed until clarification is received
4. Execute with Context: Use original intent + clarifications + research findings

Evaluation Criteria

Prompts are scored on:

• Target Specificity: Does it mention specific files, functions, or components?
• Action Clarity: Is the action clearly defined with specifics?
• Success Criteria: Are expected outcomes described?
• Context: Is there sufficient context to execute?

Bypass Prefixes

The following prefixes bypass evaluation:

• * - Force immediate execution
• / - Slash commands
• # - Memory/notes
• ! - Shell commands

Tools Provided

evaluate_prompt

Manually evaluate a prompt for clarity.

evaluate_prompt("fix the bug")
// Returns: { isVague: true, score: 15, reasons: [...], suggestions: [...] }

improve_prompt

Generate improvement context for a vague prompt.

improve_prompt("add authentication")
// Returns detailed research and clarification instructions

Examples

Vague Prompt (Triggers Clarification)

User: "fix the bug"

Plugin injects context instructing agent to:
1. Search for TODOs, failing tests, recent commits
2. Ask which specific bug to fix with options from codebase
3. Wait for user selection before proceeding

Clear Prompt (Passes Through)

User: "Refactor getUserById in src/api/users.ts to use async/await"

Plugin: Score 85/100 - Clear enough, no clarification needed

Development

# Install dependencies
bun install

# Type check
bun tsc --noEmit

# Build
mise run build

# Test
mise run test

License

MIT