Carapace
All Guides
Social

Farcaster

Post casts and interact via the Neynar API

Farcaster Setup Guide

Enables your agent to post casts, read feeds, react, follow/unfollow, and interact with channels on Farcaster via the Neynar API.

Overview

Farcaster is a decentralized social protocol — it doesn't have a traditional REST API. Neynar is the infrastructure layer that provides API access. You need two things from Neynar: an API key (for authentication) and a Signer UUID (an authorized keypair that can post casts on behalf of your Farcaster account).

Prerequisites

  • A Farcaster account (sign up via Warpcast mobile app)
  • A Neynar account at neynar.com
  • The Warpcast mobile app installed (required to approve the signer)

Step 1: Get a Neynar API Key

  1. Go to dev.neynar.com and sign up or log in
  2. Create a new app (or use an existing one)
  3. Copy the API Key from your app dashboard

Step 2: Create a Signer

A signer is an authorized keypair that Neynar manages on your behalf. It needs to be approved by your Farcaster account through the Warpcast mobile app.

Via Neynar Dashboard (recommended)

  1. In the Neynar dashboard, go to your app
  2. Navigate to Signers section
  3. Click Create Signer
  4. A QR code or deep link will appear — scan it with the Warpcast mobile app
  5. In Warpcast, approve the signer request
  6. Back in the Neynar dashboard, the signer status will change to approved
  7. Copy the Signer UUID (format: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)

Via Neynar API (advanced)

# Create a signer
curl -X POST "https://api.neynar.com/v2/farcaster/signer" \
  -H "api_key: YOUR_NEYNAR_API_KEY" \
  -H "Content-Type: application/json"

# Response includes signer_uuid and signer_approval_url
# Open signer_approval_url in Warpcast to approve

After approval, the signer_uuid is ready to use.

Step 3: Connect in Carapace

  1. Go to Dashboard > Connections
  2. Find Farcaster and click Connect
  3. Fill in:
    • API Key — your Neynar API key
    • Signer UUID — the approved signer UUID from Step 2
  4. Click Save Credentials

Credential Fields Reference

FieldRequiredFormatDescription
api_keyYesStringNeynar API key from your app dashboard
signer_uuidYesUUID (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)Neynar signer authorized to act on your Farcaster account

Gotchas

Signer approval requires Warpcast mobile app: You cannot approve a signer from a desktop browser. The Warpcast mobile app is required for the approval flow. Have your phone ready when creating the signer.

Signer UUID is NOT your FID: Your Farcaster ID (FID) is a number like 12345. The signer UUID is a Neynar-generated identifier for the authorized keypair. They are completely different values.

Neynar free tier rate limits: The free tier has request limits that may affect high-frequency agent usage. Check Neynar pricing for current limits.

Signer can be revoked: If you revoke the signer in Warpcast settings or the Neynar dashboard, the agent will lose write access. Read operations (feed, search) still work with just the API key.

One signer per Farcaster account per app: Each Neynar app typically uses one signer per Farcaster account. If you create a new signer for the same account, the old one may still work unless explicitly revoked.

Troubleshooting

"Signer not found" or "Signer not approved"

The signer UUID either doesn't exist or hasn't been approved in Warpcast. Go to the Neynar dashboard, check the signer status, and re-approve if needed.

Casts not appearing

The cast may have been posted successfully but not yet indexed. Farcaster hub propagation can take a few seconds. Also verify you're looking at the correct Farcaster account (the one that approved the signer).

401 on all requests

Your Neynar API key is invalid or expired. Regenerate it from the Neynar dashboard.

See Also