farcaster

name	farcaster
description	Post, read, search, and engage on Farcaster via the Neynar API. Use when an agent needs to post casts, read feeds, search casts, look up users, like/recast, or interact with channels. Activate for any Farcaster social media interaction or Web3 social protocol query.

Farcaster

Interact with Farcaster — the decentralized social protocol — via the Neynar v2 REST API.

Setup

export NEYNAR_API_KEY="your-api-key"        # required for all ops
export NEYNAR_SIGNER_UUID="your-signer-uuid"  # required for write ops

Get API key at https://neynar.com

API

Base: https://api.neynar.com/v2/farcaster

Read Operations (Free tier)

User's casts by FID:

web_fetch url="https://api.neynar.com/v2/farcaster/feed/user/3?limit=10" headers="api_key: NEYNAR_API_KEY"

User lookup by username:

web_fetch url="https://api.neynar.com/v2/farcaster/user/by_username?username=vitalik" headers="api_key: NEYNAR_API_KEY"

User lookup by FID:

web_fetch url="https://api.neynar.com/v2/farcaster/user/bulk?fids=3" headers="api_key: NEYNAR_API_KEY"

Cast thread/replies:

web_fetch url="https://api.neynar.com/v2/farcaster/cast/conversation?identifier=0xHASH&type=hash" headers="api_key: NEYNAR_API_KEY"

Write Operations (Require signer)

Post a cast:

exec command="curl -s -X POST 'https://api.neynar.com/v2/farcaster/cast' -H 'api_key: NEYNAR_API_KEY' -H 'Content-Type: application/json' -d '{\"signer_uuid\":\"SIGNER_UUID\",\"text\":\"Hello Farcaster!\"}'"

Post to a channel:

exec command="curl -s -X POST 'https://api.neynar.com/v2/farcaster/cast' -H 'api_key: NEYNAR_API_KEY' -H 'Content-Type: application/json' -d '{\"signer_uuid\":\"SIGNER_UUID\",\"text\":\"gm\",\"channel_id\":\"base\"}'"

Reply to a cast:

exec command="curl -s -X POST 'https://api.neynar.com/v2/farcaster/cast' -H 'api_key: NEYNAR_API_KEY' -H 'Content-Type: application/json' -d '{\"signer_uuid\":\"SIGNER_UUID\",\"text\":\"Great point!\",\"parent\":\"0xHASH\"}'"

Like a cast:

exec command="curl -s -X POST 'https://api.neynar.com/v2/farcaster/reaction' -H 'api_key: NEYNAR_API_KEY' -H 'Content-Type: application/json' -d '{\"signer_uuid\":\"SIGNER_UUID\",\"reaction_type\":\"like\",\"target\":\"0xHASH\"}'"

Search (Paid tier)

Search casts by keyword:

web_fetch url="https://api.neynar.com/v2/farcaster/cast/search?q=ethereum&limit=10" headers="api_key: NEYNAR_API_KEY"

Search channels:

web_fetch url="https://api.neynar.com/v2/farcaster/channel/search?q=defi" headers="api_key: NEYNAR_API_KEY"

Free vs Paid

Feature	Free
Post cast	Yes
User lookup	Yes
User feed	Yes
Like/recast	Yes
Following feed	Yes
Cast search	Paid
Channel feed	Paid
Channel search	Paid

Rate limit: 300 req/min (free tier)

Use Cases

• Agent social presence: post updates, market alerts, DeFi insights to Farcaster
• Community monitoring: track mentions, replies, and channel activity
• Social signals: correlate social engagement with token performance
• Agent-to-agent: coordinate with other agents via Farcaster channels