MCP server for Harness FME (Split.io) — read and toggle feature flags.

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Features

• 30 tools — covers workspaces, environments, feature flags, flag definitions, segments, rule-based segments, and change requests.
• Kill & restore — instantly kill a flag to force all traffic to the default treatment, or restore it with a single tool call.
• Safety guard — every destructive operation (delete, kill, archive, disable) requires confirm: true, preventing accidental changes.
• Rule-based segments — create, update, enable, disable, and submit change requests for rule-based segments per environment.
• Change request flow — submit segment definition changes with optional approvers for teams that require approval gates.
• Zero-config startup — reads MCP_HARNESS_FME_API_KEY from the environment and exits immediately if it is missing.

Install

Add to your MCP client config (see Usage below), or install globally to run manually:

npx --yes @kud/mcp-harness-fme@latest

Set the environment variable MCP_HARNESS_FME_API_KEY to your Harness FME API key before starting the server.

Usage

This is a standard stdio MCP server — it works with any MCP client (Claude Desktop, Claude Code, Cursor, Windsurf, Cline, Zed, …). Add it to your client's MCP config:

{
  "mcpServers": {
    "harness-fme": {
      "command": "npx",
      "args": ["--yes", "@kud/mcp-harness-fme@latest"],
      "env": {
        "MCP_HARNESS_FME_API_KEY": "your_api_key"
      }
    }
  }
}

Most clients read this mcpServers shape — Claude Desktop's config file, Cursor's .cursor/mcp.json, Windsurf, Cline, and so on. For Claude Code, there's a CLI shortcut:

claude mcp add --transport stdio --scope user harness-fme \
  --env MCP_HARNESS_FME_API_KEY=your_api_key \
  -- npx --yes @kud/mcp-harness-fme@latest

To enable the get_flag_url deep-link tool, also set two optional keys — add them to the env block above (or as extra --env flags for the CLI). See Configuration for where to find their values.

"env": {
  "MCP_HARNESS_FME_API_KEY": "your_api_key",
  "MCP_HARNESS_FME_ACCOUNT_ID": "your_account_id",
  "MCP_HARNESS_FME_ORG_GUID": "your_org_guid"
}

Leave them out and every other tool still works — get_flag_url just reports what's missing.

Available tools

| Tool | Description | | ------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | list_workspaces | List all FME workspaces in the account | | list_environments | List all environments in a workspace | | list_traffic_types | List all traffic types in a workspace | | list_rollout_statuses | List rollout status definitions for a workspace | | list_feature_flags | List feature flags in a workspace (filter by tag, status, name) | | get_feature_flag | Get metadata for a specific feature flag | | create_feature_flag | Create a new feature flag for a given traffic type | | update_feature_flag | Update a flag's description, tags, owners, or rollout status | | delete_feature_flag | Permanently delete a feature flag (confirm: true required) | | archive_feature_flag | Archive a flag, removing it from active use (confirm: true required) | | unarchive_feature_flag | Restore a previously archived feature flag | | kill_feature_flag | Kill a flag in an environment — forces default treatment (confirm: true required) | | restore_feature_flag | Restore a killed feature flag in an environment | | list_flag_definitions | List flag targeting rules in an environment | | get_flag_definition | Get treatments and targeting rules for a flag in an environment | | create_flag_definition | Activate a flag in an environment with treatments and targeting rules — pass title/comment when requiresTitleAndComments: true | | update_flag_definition | Fully replace a flag's targeting rules in an environment — pass title/comment when requiresTitleAndComments: true | | delete_flag_definition | Remove a flag's targeting rules from an environment (confirm: true required) | | add_segment_to_treatment | Add a segment to a flag treatment via safe read-modify-write (idempotent; avoids full-replace) — pass title/comment when requiresTitleAndComments: true | | get_flag_url | Build a Harness FME web-UI deep-link for a flag — pass workspace/flag/environment by name or id (needs two MCP_HARNESS_FME_* env vars, see Configuration) | | list_segments | List all segments in a workspace (API caps page size at 20) | | list_rule_based_segments | List all rule-based segments in a workspace | | get_rule_based_segment | Get a rule-based segment's workspace-level metadata | | create_rule_based_segment | Create a new rule-based segment in a workspace | | delete_rule_based_segment | Permanently delete a rule-based segment (confirm: true required) | | list_rule_based_segment_definitions | List rule-based segment definitions in an environment | | update_rule_based_segment_definition | Update a rule-based segment's rules in an environment | | enable_rule_based_segment_definition | Activate a rule-based segment in an environment | | disable_rule_based_segment_definition | Remove a rule-based segment from an environment (confirm: true required) | | create_rule_based_segment_change_request | Submit a change request for a segment definition with optional approval flow |

Configuration

The server reads these environment variables:

| Variable | Required? | Used by | | ---------------------------- | ------------ | ---------------------------------------------- | | MCP_HARNESS_FME_API_KEY | Required | Every tool — server exits at startup if absent | | MCP_HARNESS_FME_ACCOUNT_ID | Optional | get_flag_url only | | MCP_HARNESS_FME_ORG_GUID | Optional | get_flag_url only |

The account ID and org GUID are Harness platform identifiers that the API does not expose, so get_flag_url reads them from env. Grab them once from any flag's URL in the Harness FME web UI:

https://app.harness.io/ng/account/<ACCOUNT_ID>/all/fme/orgs/<ORG_SLUG>/projects/<PROJECT>/org/<ORG_GUID>/ws/<WORKSPACE_ID>/splits/<FLAG_ID>/env/<ENV_ID>/definition

| URL segment | Where it goes | | -------------------------------- | ------------------------------------------------------------------------------------------- | | /account/<ACCOUNT_ID> | → MCP_HARNESS_FME_ACCOUNT_ID env var | | /org/<ORG_GUID> (singular) | → MCP_HARNESS_FME_ORG_GUID env var | | /orgs/<ORG_SLUG> (plural) | Resolved by get_flag_url from the workspace — not an env var | | /ws/… · /splits/… · /env/… | Resolved by get_flag_url from the workspace / flag / environment you pass (by name or id) |

⚠ The URL has two org-ish segments: /orgs/ (plural) is the human slug; /org/ (singular) is the GUID you want for MCP_HARNESS_FME_ORG_GUID. Grab the singular one.

With those two set, get_flag_url needs only a workspace, flag, and environment (name or id) — it resolves everything else. Without them, it returns a message telling you what to set, and every other tool works normally.

Development

git clone https://github.com/kud/mcp-harness-fme.git
cd mcp-harness-fme
npm install
npm run dev           # run from source with tsx
npm run inspect:dev   # MCP Inspector at http://localhost:5173
npm test              # vitest
npm run build         # compile to dist/

Environment variables are documented in Configuration above. All tools are defined in src/index.ts.

📚 Full documentation → mcp-harness-fme/docs