Flag Prerequisites

flag-prerequisites

Add, remove, or inspect feature-level prerequisites on a GrowthBook feature flag. A feature-level prerequisite is a boolean gate: if the specified prerequisite flag is off for a user, the current flag skips all its rules and returns its defaultValue for that user.

Feature-level prerequisites are boolean-flag-only. The prerequisite flag must have valueType: "boolean". The gate condition is always "prerequisite flag is on" ({"value": true}) — no custom conditions. If the user wants a more nuanced dependency (e.g. gate on a string flag's value, or gate a single rule rather than the whole flag), route to flag-targeting.

This is distinct from rule-level prerequisites (which gate a single rule and support richer conditions) — feature-level prerequisites apply to every rule on the flag simultaneously.

All API calls go through the bundled helper: ${CLAUDE_PLUGIN_ROOT}/scripts/gb-call. It needs GB_API_KEY set in env or written to ~/.config/growthbook/.env by /growthbook:setup.

Workflow

Path A — Add a prerequisite

1. Fetch the flag's current prerequisites:

``bash gb-call GET /api/v2/features/ ` Capture the existing prerequisites` array. The PUT below replaces the full array, so you need the current contents to avoid overwriting existing prerequisites.

1. Confirm the prerequisite flag exists and is boolean:

``bash gb-call GET /api/v2/features/ ` Check valueType. If it is not "boolean", halt: > "Feature-level prerequisites only support boolean flags. is a ` flag. To gate on a non-boolean flag's value, add a rule-level prerequisite instead via flag-targeting."

1. Build the new prerequisites array. Append to any existing entries. The condition is always {"value": true} — the gate means "prerequisite flag is on":

``json [ { "id": "", "condition": "{\"value\": true}" }, { "id": "", "condition": "{\"value\": true}" } ] ``

1. Apply via draft:

``bash echo '{"prerequisites":[...]}' \ | gb-call PUT /api/v2/features//revisions/new/prerequisites - ``

1. Hand off to flag-publish.

Path B — Remove a prerequisite

1. Fetch current prerequisites (step A-1 above).
2. Show the list and ask which to remove.
3. Build the updated array without the removed entry.
4. Apply via draft (step A-4 above) with the filtered array. An empty array [] removes all prerequisites.
5. Hand off to flag-publish.

Path C — Inspect current prerequisites

gb-call GET /api/v2/features/

Surface the prerequisites array. For each entry, fetch the prerequisite flag to show its current evaluated state and value type. Use flag-graph to trace the full dependency chain if needed.

Guardrails

• Draft version threading. If a version number is already in context from a previous write skill in this session, use it explicitly (e.g. .../revisions/42/prerequisites) instead of new. This keeps all changes in the same draft. Fall back to new when starting fresh — it auto-creates or reuses the most recently updated open draft.
• PUT /prerequisites replaces the full array. It's not additive. Always fetch the current array first and include all existing entries when adding or modifying — otherwise you'll silently delete prerequisites the user didn't intend to touch.
• Prerequisite flags must be boolean. Halt and route to flag-targeting if the user specifies a non-boolean flag as a prerequisite.
• The condition is always {"value": true}. Do not accept or generate custom conditions for feature-level prerequisites. The backend is permissive but we intentionally constrain this — the gate means "this flag is on". If the user wants a richer condition (e.g. string flag equals a value, flag is live but not necessarily true), route to flag-targeting rule-level prerequisites.
• Feature-level vs rule-level prerequisites. This skill gates the entire flag. If the user wants a prerequisite scoped to a single rule, route to flag-targeting.
• Circular dependencies must be avoided. If flag A requires flag B and flag B requires flag A, neither will ever evaluate. Check the existing dependency chain via flag-graph before adding a prerequisite.
• Prerequisite flags must be in the same GrowthBook project (or org-wide). Cross-project prerequisites may not resolve correctly depending on SDK configuration.
• Deleting a prerequisite flag breaks any flag that depends on it. The dependent flag's prerequisite condition will silently always fail. Surface this when the user is reviewing dependencies via flag-graph before cleanup.

Endpoints used

• GET /api/v2/features/:id — fetch flag state including current prerequisites array
• PUT /api/v2/features/:id/revisions/new/prerequisites (body: { "prerequisites": [...] })

Handoffs

• flag-search — to find the prerequisite flag's ID if the user gives a name
• flag-graph — to trace the full dependency chain and detect circular dependencies
• flag-targeting — to add rule-level prerequisites (scoped to a single rule rather than the whole flag)
• flag-publish — to publish the draft, handle approval-required (400) and merge conflicts (409)

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: growthbook
• Source: growthbook/skills
• License: MIT

Install and usage instructions live in the source repository linked above.