Model Context Protocol (MCP) server for Splera — A/B testing for vibe coders. Create experiments, check results, and ship winners directly from your AI coding agent.
A/B testing for vibe coders, exposed as a Model Context Protocol (MCP) server. Your AI agent creates experiments, reads results, and ships winners without you leaving chat.
Three native tools your agent gets once installed: create_experiment, get_results, ship_winner. The agent calls them, edits your code to wire the SDK and variant, and reports stats back in plain English. No dashboard tab, no copy-paste, no test infrastructure to learn.
splera-mcpOnce installed, paste any of these into your agent:
Create a Splera A/B test for my homepage headline: 'Ship faster.' vs 'Ship with confidence.'
How's my checkout experiment doing?
Ship the winning variant.
The agent picks the right tool, makes the call, and either edits your code to install the SDK, reports Bayesian stats in human terms, or flips the winning variant server-side (takes effect in ~30 seconds worldwide, no redeploy).
Go to splera.app/settings, click Generate new key, name it something like claude-code-macbook. Copy the key from the one-time modal. It starts with splera_live_. You will not see the full key again. If you close the modal without copying, revoke and regenerate.
| Agent | Config file | Method |
|---|---|---|
| Claude Code | ~/.config/claude-code/mcp.json | One-liner (below) or edit JSON |
| Cursor | ~/.cursor/mcp.json | Edit JSON (or Settings → MCP) |
| Windsurf | ~/.codeium/windsurf/mcp_config.json | Edit JSON |
| Zed | ~/.config/zed/settings.json (context_servers block) | Edit JSON |
| Replit Agent | Not supported in v1 (cloud-hosted, can't load local stdio MCP) | — |
claude mcp add splera npx -y splera-mcp@latest --env SPLERA_API_KEY=splera_live_your_key_here
Then restart Claude Code.
Same JSON shape for both, just different file paths.
{
"mcpServers": {
"splera": {
"command": "npx",
"args": ["-y", "splera-mcp@latest"],
"env": {
"SPLERA_API_KEY": "splera_live_your_key_here"
}
}
}
}
Restart the agent.
Add to ~/.config/zed/settings.json:
{
"context_servers": {
"splera": {
"command": {
"path": "npx",
"args": ["-y", "splera-mcp@latest"],
"env": { "SPLERA_API_KEY": "splera_live_your_key_here" }
}
}
}
}
Restart Zed.
curl -H "Authorization: Bearer splera_live_your_key_here" https://splera.app/api/me
200 OK with a JSON body means the key works. 401 means the key is bad or revoked, regenerate at splera.app/settings.
Open your agent's Server logs or MCP panel. You should see:
splera-mcp: connecting to https://splera.app
splera-mcp: ready. 3 tools loaded. User: you@example.com
If those lines are missing, the MCP isn't loading. Check your config file path and JSON syntax.
The MCP config isn't being read. Check that (1) you edited the right file for your agent (see install table above), (2) the JSON is valid, no trailing commas, (3) you restarted the agent after editing.
SPLERA_API_KEY not setThe env block in your MCP config is missing or malformed. The key must start with splera_live_. Re-check the examples above.
SPLERA_INVALID_API_KEY on every callThe key is wrong, revoked, or truncated during copy. Go to splera.app/settings, revoke the existing key, generate a new one, update the config, restart the agent.
SPLERA_PLAN_LIMIT_EXCEEDED on create_experimentYou've hit your plan's monthly experiment cap. Options: upgrade or ship / stop an existing experiment to free a slot. The error hint field tells you which plan and how many slots are used.
get_results says NOT_READY foreverThe SDK isn't reaching the page being tested. Verify the script tag is in place:
<script src="https://splera.app/sdk/splera.js" data-experiment-id="YOUR-EXPERIMENT-UUID" async></script>
Also confirm the page is receiving real traffic. The dashboard shows live exposure counts at splera.app/experiments/:id.
Most agents need explicit mentions of the tool until it's familiar. Try prompts like "use the splera MCP to create an experiment" instead of generic "set up an A/B test". Once the agent calls it once, it remembers.
create_experimentCreate a new A/B test. Returns the experiment ID, variant IDs, and an SDK install snippet the agent can paste into your codebase.
Required: name (3-80 chars), hypothesis (10-500 chars), variants (2-5 items, control first), metrics (1-5 items, each with name + event_name).
Optional: decision_mode (quick_decision / rigorous / bandit, default quick_decision), platform (replit / lovable / bolt / claude_design / other, default other).
Example prompt:
Create a Splera experiment on my pricing page — test "Start free" vs "Get started" on the primary CTA. Primary metric is signup_completed.
get_resultsFetch current results for an experiment. Returns variant stats, Bayesian leader probability, ship-readiness verdict, and (post-ship) guard-window status. Safe to call once per minute during active experiments. For long-horizon monitoring, use the dashboard.
Required: experiment_id (UUID from create_experiment).
The response includes a next_check_recommended_at timestamp so the agent knows when it's worth checking again, instead of spamming the endpoint.
Example prompt:
How's my hero CTA experiment doing? Ready to ship?
ship_winnerShip the winning variant to 100% of traffic. The SDK flips server-side within 30 seconds worldwide. No redeploy, no code change on your end. After shipping, a guard window monitors the live rate against a frozen pre-ship baseline and emails you if performance degrades.
Required: experiment_id, winning_variant_id (the slug-style ID like variant_b or control, not the variant's display name — use leading_variant_id from get_results).
Example prompt:
Ship variant_b on experiment 7f3e9a2b.
splera-mcp makes HTTPS calls to splera.app only. No local telemetry, no third-party analytics from this package.sha256 hashes in our database. Even if our DB were compromised, the raw keys are not recoverable.Built by Splera. A/B testing for vibe coders.
FAQs
Model Context Protocol (MCP) server for Splera — A/B testing for vibe coders. Create experiments, check results, and ship winners directly from your AI coding agent.
The npm package splera-mcp receives a total of 18 weekly downloads. As such, splera-mcp popularity was classified as not popular.
We found that splera-mcp demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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