mcp-circuit-breaker git:20260528.588563eA

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---
name: mcp-circuit-breaker
description: Detects MCP tool failure patterns and trips a circuit breaker to stop cascading retries. Proposes fallback alternatives and resets when the tool recovers. Triggers on "MCP failing", "tool keeps erroring", "circuit-breaker", repeated tool call failures.
user-invocable: true
allowed-tools: ["Read", "Bash", "Write"]
model: sonnet
complexity_routing:
  base: sonnet
  high: opus
  escalate_when:
    - multi_server_failure
    - unknown_mcp_server
---

# mcp-circuit-breaker — MCP Tool Failure Guard

MCP tools can fail silently or return partial results, leading to cascading retry loops that waste tokens and degrade session quality. This skill detects failure patterns, trips a circuit breaker to halt retries, proposes alternatives, and resets when the tool recovers.

> **Scope distinction**
> - Claude Code native retry: low-level transport retries (transparent, fast)
> - mcp-circuit-breaker: **session-level guard** — detects repeated semantic failures, intervenes before token waste compounds

---

## Triggers

- `/mcp-circuit-breaker`
- "MCP failing", "MCP keeps erroring", "tool isn't working", "circuit-breaker"
- "same error keeps happening", "tool call looping", "MCP timeout"
- Automatic: when the same MCP tool name appears in 3+ consecutive failed calls within a session

---

## Circuit States

```
CLOSED   → Normal operation (tool calls pass through)
OPEN     → Circuit tripped (calls blocked, alternatives proposed)
HALF-OPEN → Recovery probe (1 test call allowed, resets if success)
```

Default thresholds:
- **Trip threshold**: 3 consecutive failures of the same tool
- **Half-open probe**: after 60s cooldown (or explicit user command)
- **Reset**: 1 successful call in HALF-OPEN state → back to CLOSED

---

## Execution Steps

### Step 1. Detect Failure Pattern

Identify the failing tool and failure mode:

```bash
# Check MCP server config
cat .claude/settings.json 2>/dev/null | grep -A5 '"mcpServers"' || echo "No MCP config found"
```

Classify failure type:

| Type | Symptom | Likely Cause |
|---|---|---|
| `TIMEOUT` | Tool call hangs >30s | Server overload / network |
| `AUTH` | 401 / 403 response | Credentials expired or missing |
| `NOT_FOUND` | 404 / tool not available | Server down / tool removed |
| `MALFORMED` | Parse error on response | Schema mismatch / API change |
| `RATE_LIMIT` | 429 / quota exceeded | Too many calls |

If failure type cannot be determined: classify as `UNKNOWN`.

---

### Step 2. Trip Decision

Count consecutive failures of the identified tool in the current session context.

| Count | Action |
|---|---|
| 1 | Log warning. Continue — *"MCP tool {name} failed once. Monitoring."* |
| 2 | Escalate warning. Suggest checking server status. |
| 3+ | **TRIP CIRCUIT** → output circuit open notice, block further calls to this tool |

Circuit open notice format:
```
⚡ CIRCUIT OPEN — {tool-name}
Failure type: {TYPE}  |  Consecutive failures: {N}
Further calls to this tool are blocked until circuit resets.
```

---

### Step 3. Log Circuit State

Write state to session-local file (in-memory is insufficient — logs survive /clear):

```bash
mkdir -p .claude/mcp_circuit/
# Append to circuit log
```

Log entry format:
```yaml
- tool: {tool-name}
  state: OPEN
  failure_type: {TYPE}
  failure_count: {N}
  tripped_at: {ISO-8601}
  reset_at: null
```

---

### Step 4. Propose Alternatives

Present 3 fallback options ranked by effort:

| Priority | Alternative | When to Use |
|---|---|---|
| **1 — Substitute tool** | Use a different MCP tool or built-in tool that covers the same task | Tool-specific failure (NOT_FOUND, AUTH) |
| **2 — Degrade gracefully** | Skip the MCP step, note the gap, continue with available information | TIMEOUT / RATE_LIMIT |
| **3 — Pause and retry** | Wait for server recovery (HALF-OPEN probe after cooldown) | Transient failure (TIMEOUT, RATE_LIMIT) |

Output format:
```
## Fallback Options for {tool-name}

Option 1 — Substitute: Use {alternative-tool} instead
  → Command: [specific invocation]
  → Gap: [what's different vs. original tool]

Option 2 — Degrade: Skip this step, continue without {capability}
  → Impact: [what is missing from the output]

Option 3 — Retry after cooldown (60s)
  → Run: /mcp-circuit-breaker reset {tool-name}
```

---

### Step 5. Recovery Probe (HALF-OPEN)

When user requests reset or after cooldown:

```
Sending HALF-OPEN probe to {tool-name}...
```

- 1 minimal test call is allowed through
- If success: circuit → CLOSED, log updated
- If fail: circuit remains OPEN, cooldown resets

Reset log entry:
```yaml
  state: CLOSED
  reset_at: {ISO-8601}
  reset_method: probe_success | user_forced
```

---

### Step 6. Report

At session end or on demand:

```
## MCP Circuit Breaker Report

| Tool | State | Failures | Tripped | Reset |
|---|---|---|---|---|
| {tool} | OPEN | 4 | 14:23 | — |
| {tool} | CLOSED | 1 | 14:10 | 14:15 (probe) |

Recommendations:
- {tool}: AUTH failure → refresh credentials in .claude/settings.json
```

---

## Done When

- Failure pattern classified (type + count)
- Circuit state logged (OPEN / HALF-OPEN / CLOSED)
- At least 3 fallback alternatives proposed when circuit is OPEN
- Recovery probe offered with reset path

---

## Chains

**Upstream** (can trigger this skill):
- Automatically activates on 3+ consecutive MCP failures during any task

**Downstream** (after circuit open):
- No mandatory chain — fallback options are presented, user decides
- Optional: `context-doctor` if MCP failure is due to large context degrading tool calls