What can you do with this server?

The Claude Error Collector is an MCP server that helps Claude learn from user corrections by recording them as rules in CLAUDE.md files. * Record corrections (record_error): Saves what was wrong, the correct approach, and a derived rule into the appropriate CLAUDE.md, with optional category tagging * Automatic file selection: Intelligently writes to a project-specific CLAUDE.md or the global ~/.claude/CLAUDE.md based on context * List learned rules (list_errors): Displays all recorded rules with filtering by category and grouping options * Delete rules: Remove specific rules by index or substring match * Update rules: Modify the text, date, and/or category of existing rules * Review rules: Assess rule age to assist with lifecycle management * Duplicate detection: Prevents redundant rules via server-side substring matching and semantic evaluation by Claude * Legacy format support: Compatible with existing CLAUDE.md files that lack metadata

How do I use Claude Error Collector?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Claude Error Collector Record that I prefer async/await over .then() chains for all API calls" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

Claude Error Collector

An MCP server for Claude Code that learns from your corrections. When you tell Claude "that was wrong" or "no, do it like this", it records the lesson as a rule in your CLAUDE.md - so the same mistake doesn't happen twice.

How It Works

You correct Claude during a coding session
Claude recognizes the correction and calls the record_error tool
The server derives a rule and writes it to the appropriate CLAUDE.md
Claude reads that rule in future sessions and avoids repeating the mistake

The server automatically detects whether you're in a project directory (writes to project CLAUDE.md) or your home directory (writes to ~/.claude/CLAUDE.md).

Tools

`record_error`

Records a correction and saves it as a learned rule with metadata (date, category).

Parameter	Type	Required	Description
`error_description`	string	yes	What was wrong
`correction`	string	yes	What is correct
`rule`	string	yes	Derived guideline, e.g. "ALWAYS use X instead of Y"
`category`	string	no	Rule category (e.g. "n8n", "bash", "google-workspace"). Auto-detected if omitted.
`project_dir`	string	no	Current working directory (for finding project CLAUDE.md)

`list_errors`

Lists all learned rules from the relevant CLAUDE.md. Supports filtering and grouping.

Parameter	Type	Required	Description
`category`	string	no	Filter rules by category
`grouped`	boolean	no	Group rules by category with headings
`project_dir`	string	no	Current working directory

`delete_rule`

Deletes a learned rule by index or substring match.

Parameter	Type	Required	Description
`index`	number	no*	1-based index of the rule to delete
`match`	string	no*	Substring to match (must match exactly one rule)
`project_dir`	string	no	Current working directory

*Exactly one of index or match must be provided.

`update_rule`

Updates an existing rule's text, date, and optionally category.

Parameter	Type	Required	Description
`index`	number	no*	1-based index of the rule to update
`match`	string	no*	Substring to match (must match exactly one rule)
`new_rule`	string	yes	The new rule text
`category`	string	no	New category (keeps existing if omitted)
`project_dir`	string	no	Current working directory

*Exactly one of index or match must be provided.

`review_rules`

Reviews all rules with their age for lifecycle management.

Parameter	Type	Required	Description
`older_than_days`	number	no	Threshold in days to consider "old" (default: 30)
`project_dir`	string	no	Current working directory

Output Format

Rules are stored in a ## Learned Rules section in your CLAUDE.md with metadata as HTML comments:

## Learned Rules

- Legacy rule without metadata (still supported)

### N8n

- Bei n8n IMMER nodeId verwenden <!-- @date:2026-02-15 @category:n8n -->

### Bash

- NEVER embed large JSON inline in Bash commands <!-- @date:2026-02-20 @category:bash -->

Metadata fields:

@date:YYYY-MM-DD — when the rule was created/updated
@category:name — rule category for grouping

Rules without metadata (legacy format) remain fully supported and appear at the top of the section without a category heading.

Installation

git clone https://github.com/henningziech/claude-error-collector-mcp.git
cd claude-error-collector-mcp
npm install && npm run build
claude mcp add error-collector -s user -- node "$PWD/dist/index.js"

Restart Claude Code after installation. No manual CLAUDE.md editing needed — the server provides its own instructions to Claude via MCP server metadata.

CLAUDE.md Resolution

The server finds the right CLAUDE.md using this logic:

If project_dir is provided: walk up the directory tree looking for CLAUDE.md
If found and not in the home directory: use it (project-level rules)
Fallback: ~/.claude/CLAUDE.md (global rules)

Duplicate Detection

Duplicate detection works on two levels:

Server-side: Before writing a rule, the server checks existing rules using case-insensitive substring matching. If the new rule is already covered by an existing one (or vice versa), it skips the write.
Semantic (via instructions): The server instructs Claude to review existing learned rules for semantic equivalence before calling record_error — even if the wording differs. Claude will:
- Skip silently if the rule clearly already exists
- Record it if the rule is clearly new
- Ask the user if a similar rule exists but it's not 100% clear whether it's a duplicate, offering options to add alongside, consolidate, or skip