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

1. You correct Claude during a coding session
2. Claude recognizes the correction and calls the record_error tool
3. The server derives a rule and writes it to the appropriate CLAUDE.md
4. 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:

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

Duplicate Detection

Duplicate detection works on two levels:

1. 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.

2. 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

License

MIT