trace-forge-mcp

MCP server for writing structured traces, spans, and decisions. The only write-path observability MCP — all 9 existing observability MCPs are read-only.

Built for EU AI Act traceability compliance (Article 14, due August 2026).

Install

npx trace-forge-mcp

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "trace-forge": {
      "command": "npx",
      "args": ["trace-forge-mcp"]
    }
  }
}

From source

git clone https://github.com/mdfifty50-boop/trace-forge-mcp.git
cd trace-forge-mcp
npm install
node src/index.js

Tools

trace_start

Begin a new trace for an agent task.

| Param | Type | Required | Description | |-------|------|----------|-------------| | agent_id | string | yes | Unique agent identifier | | task_description | string | yes | What the agent is doing | | metadata | object | no | Optional metadata (model, department, priority) |

Returns: { trace_id, started_at }

trace_span

Create a span within a trace. Spans can be nested via parent_span_id.

| Param | Type | Required | Description | |-------|------|----------|-------------| | trace_id | string | yes | Trace to attach to | | span_name | string | yes | Span name (e.g. "research", "validation") | | parent_span_id | string | no | Parent span for nesting | | metadata | object | no | Optional span metadata |

Returns: { span_id, trace_id }

trace_tool_call

Log a tool call within a trace. Auto-calculates cost estimate from token count.

| Param | Type | Required | Description | |-------|------|----------|-------------| | trace_id | string | yes | Trace this belongs to | | span_id | string | no | Span this belongs to | | tool_name | string | yes | Tool that was called | | args | object | yes | Arguments passed | | result_preview | string | yes | Result preview (max 500 chars) | | tokens_used | number | no | Token count (enables cost estimation) | | duration_ms | number | yes | Call duration in milliseconds | | status | string | yes | "success", "error", or "timeout" |

Returns: { event_id, logged: true }

trace_decision

Log an agent decision point with reasoning and alternatives considered.

| Param | Type | Required | Description | |-------|------|----------|-------------| | trace_id | string | yes | Trace this belongs to | | reasoning | string | yes | Why the agent made this decision | | alternatives_considered | string[] | yes | Other options evaluated | | chosen_action | string | yes | What was decided | | confidence | number | yes | Confidence 0.0 to 1.0 |

Returns: { event_id, logged: true }

trace_end

Complete a trace. Auto-calculates total duration, event counts, and span counts.

| Param | Type | Required | Description | |-------|------|----------|-------------| | trace_id | string | yes | Trace to complete | | outcome | string | yes | "success", "failure", "partial", or "timeout" | | summary | string | no | Optional summary |

Returns: { trace_id, duration_ms, events_count, spans_count, tool_calls_count }

get_trace

Retrieve a complete trace tree with all spans, events, tool calls, and decisions.

| Param | Type | Required | Description | |-------|------|----------|-------------| | trace_id | string | yes | Trace ID to retrieve |

Returns: Full trace object with nested span tree, all events, and computed totals.

search_traces

Find traces by agent ID and/or status.

| Param | Type | Default | Description | |-------|------|---------|-------------| | agent_id | string | - | Filter by agent | | status | string | - | Filter by status | | limit | number | 20 | Max results (1-100) |

Returns: Matching traces sorted by recency with summary stats.

Resources

| URI | Description | |-----|-------------| | traces://recent | Last 20 traces with summary | | traces://stats | Aggregate statistics (total, avg duration, success rate) |

Usage Pattern

1. trace_start — when agent begins a task
2. trace_span — create logical work units (research, generation, validation)
3. During execution:
   - trace_tool_call — after each tool invocation
   - trace_decision — at each decision point
4. trace_end — when task completes
5. get_trace — retrieve full audit trail
6. search_traces — find traces by agent or status

EU AI Act Compliance

Article 14 of the EU AI Act requires high-risk AI systems to maintain traceability of decisions and actions. trace-forge-mcp provides:

• Structured decision logging with reasoning and alternatives
• Complete tool call audit trails with timing and cost
• Hierarchical span trees for complex multi-step tasks
• Agent identification and task attribution

License

MIT