---
name: langsmith-fetch
description: Fetches LangSmith traces for debugging agent behavior. Use when troubleshooting agent issues, reviewing conversation history, or investigating tool calls.
---

# Fetching LangSmith Traces

Requires `langsmith-fetch` in project dependencies and `LANGSMITH_API_KEY` in a `.env` file.

## Setup

First, find the `.env` file containing `LANGSMITH_API_KEY`:
```bash
find . -name ".env" -type f 2>/dev/null | head -5
```

## Commands

Use `--env-file <path-to-.env>` with all commands:

```bash
# Fetch recent traces (uses LANGSMITH_PROJECT from .env, or specify --project-uuid)
uv run --env-file <path> langsmith-fetch traces ./traces --limit 10
uv run --env-file <path> langsmith-fetch traces ./traces --project-uuid <uuid> --limit 10

# Fetch single trace by ID
uv run --env-file <path> langsmith-fetch trace <trace-id>

# Include metadata (timing, tokens, costs)
uv run --env-file <path> langsmith-fetch trace <trace-id> --include-metadata
```

## Output Formats

- `--format pretty` - Human-readable (default)
- `--format json` - Pretty-printed JSON
- `--format raw` - Compact JSON for piping

## Troubleshooting Workflow

1. Find `.env`: `find . -name ".env" -type f 2>/dev/null`
2. Fetch recent traces: `uv run --env-file <path> langsmith-fetch traces ./debug --limit 10`
3. Find relevant trace in saved JSON files
4. Check: What tools were called? What did they return? Was it correct/expected?