Trace Forge

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