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LangSmith MCP Server

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An MCP server for fetching conversation history and prompts from the LangSmith observability platform.

Install
How to run this server
[ { "cmd": "npx @modelcontextprotocol/inspector@latest", "imports": [] } ]
server path: langsmith-mcp-server
Tools
What this server exposes
get_thread_history
Retrieve message history for a conversation thread. Uses char-based pagination: pass page_number (1-based), and use returned total_pages to request more pages. Optional max_chars_per_page and preview_chars control page size and long-string truncation.
list_prompts
Fetch prompts from LangSmith with optional filtering by visibility (public/private) and limit.
get_prompt_by_name
Get a specific prompt by its exact name, returning the prompt details and template.
push_prompt
Documentation-only: how to create and push prompts to LangSmith.
fetch_runs
Fetch LangSmith runs (traces, tools, chains, etc.) from one or more projects. Supports filters (run_type, error, is_root), FQL (filter, trace_filter, tree_filter), and ordering. When trace_id is set, returns char-based paginated pages; otherwise returns one batch up to limit. Always pass limit and page_number.
list_projects
List LangSmith projects with optional filtering by name, dataset, and detail level (simplified vs full).
list_datasets
Fetch datasets with filtering by ID, type, name, name substring, or metadata.
list_examples
Fetch examples from a dataset by dataset ID/name or example IDs, with filter, metadata, splits, and optional as_of version.
read_dataset
Read a single dataset by ID or name.
read_example
Read a single example by ID, with optional as_of version.
create_dataset
Documentation-only: how to create datasets in LangSmith.
update_examples
Documentation-only: how to update dataset examples in LangSmith.
list_experiments
List experiment projects (reference projects) for a dataset. Requires reference_dataset_id or reference_dataset_name. Returns key metrics (latency, cost, feedback stats).
run_experiment
Documentation-only: how to run experiments and evaluations in LangSmith.
get_billing_usage
Fetch organization billing usage (e.g. trace counts) for a date range. Optional workspace filter; returns metrics with workspace names inline.
Configuration
Environment & auth
authnone
envLANGSMITH_API_KEY
envLANGSMITH_WORKSPACE_ID
envLANGSMITH_MONITORING_API_KEY
envLANGSMITH_MONITORING_WORKSPACE_ID
Resources
LangSmith MCP Server — MCP Server · libregistry