BridgeKitty 🐱
Cross-chain bridge aggregator MCP server for AI agents. One server, 5 bridge backends, best routes across EVM, Solana, and Cosmos chains.
BridgeKitty gives AI agents (Claude, Cursor, GPT, or any MCP-compatible AI) the ability to find and execute cross-chain bridge transfers — with automatic route optimization, fee comparison, balance checks, and safety warnings.
Latest npm release: @persistenceone/bridgekitty@0.3.9
What's New in v0.3.9
- XPRT tools extracted — staking, rewards, and farming tools moved to the standalone
xprt-farming-toolkit package
- Persistence Interop backend removed — BridgeKitty is now a focused bridge aggregator across 5 backends (deBridge, Relay, LI.FI, Across, Squid)
- Slimmer surface area — fewer tools, clearer scope for agents
What's New in v0.3.0
sign_and_send parameter — agents can now sign and broadcast transactions directly using locally-stored wallet keys- Full EVM signing support — works with all EVM backends (Across, Relay, LI.FI, Squid, deBridge) + Persistence Interop (EIP-712)
- Simulation fix — ERC20 bridges now work on fresh wallets (previously blocked by premature simulation)
- Solana signing — coming in next release
What's New in v0.2.0
- Solana support — bidirectional bridging EVM ↔ Solana (native SOL delivery, not wrapped)
- Cosmos support — EVM → Persistence/Cosmos Hub via Squid (Axelar)
- Protocol fee transparency — deBridge fixFee, operating expenses, and total cost visible in every quote
- Balance warnings — warns when wallet can't cover bridge amount + protocol fees + gas
- XPRT staking — stake/unstake/claim rewards directly from the MCP server
- Farming multiplier — tracks your staking tier (1x → 3x → 5x) from the rewards API
- Quote auto-refresh — expired quotes automatically re-fetched on execute (60s expiry)
- ERC-20 approvals — always generated for token bridges (Relay + deBridge)
- Bridge status tracking — on-chain fallback when provider API hasn't indexed yet
Supported Bridges
| Backend | Type | Chains | Strength |
|---|
| deBridge (DLN) | Direct | EVM + Solana | Fast intent-based fills, Solana support |
| Relay | Direct | EVM + Solana | No protocol fee, gas-optimized |
| LI.FI | Aggregator | EVM | Widest coverage (30+ bridges, any-to-any swap) |
| Across | Direct | EVM | Fastest fills (~6s), same-token bridging |
| Squid (Axelar) | Aggregator | EVM + Cosmos | Only option for EVM → Cosmos routes |
Bridge Directions
| Direction | Backends | Status |
|---|
| EVM → EVM | All 5 | ✅ Production |
| EVM → Solana | deBridge, Relay | ✅ Production |
| Solana → EVM | deBridge | ✅ Production |
| EVM → Cosmos | Squid | ✅ Production |
Quick Start
npx (zero install)
npx @persistenceone/bridgekitty
Claude Code
Add to your MCP config (~/.claude/claude_code_config.json):
{
"mcpServers": {
"bridgekitty": {
"command": "npx",
"args": ["@persistenceone/bridgekitty"]
}
}
}
Cursor IDE
Add to Cursor's MCP settings (Settings > MCP Servers):
{
"bridgekitty": {
"command": "npx",
"args": ["@persistenceone/bridgekitty"]
}
}
Claude Desktop
Add to claude_desktop_config.json:
{
"mcpServers": {
"bridgekitty": {
"command": "npx",
"args": ["@persistenceone/bridgekitty"]
}
}
}
Wallet Setup
BridgeKitty can manage wallets for autonomous bridging. Run wallet_setup to create wallets for EVM, Cosmos, and Solana — or provide your own addresses in quotes.
Wallet config is stored in ~/.bridgekitty/.env (or the directory you run from). Keys never leave the local machine.
| Variable | Description |
|---|
PRIVATE_KEY | EVM private key (hex) |
MNEMONIC | BIP-39 mnemonic (derives EVM, Cosmos, Solana keys) |
SOLANA_PRIVATE_KEY | Solana private key (base58) |
Transaction Signing
By default, bridge_execute returns unsigned transactions for the agent or user to sign externally.
Set sign_and_send: true to enable autonomous signing — BridgeKitty will use the wallet keys stored in ~/.bridgekitty/.env to handle the full flow:
- Approval — sends ERC-20 approval transaction (if needed)
- Re-build — re-fetches the bridge transaction with updated nonce (if approval was sent)
- Simulate — runs
eth_estimateGas pre-flight check
- Sign — signs the transaction with the local private key
- Broadcast — submits to the chain and returns the tx hash + explorer link
Optional API Keys
| Variable | Description |
|---|
LIFI_API_KEY | LI.FI API key (higher rate limits) |
DEBRIDGE_API_KEY | deBridge API key |
SQUID_INTEGRATOR_ID | Squid integrator ID |
MCP Tools
Core Bridge Tools
| Tool | Description |
|---|
bridge_get_quote | Get competitive quotes from all backends. Shows fees, time estimates, balance warnings. |
bridge_execute | Build transaction(s) from a quote. Handles approvals, auto-refreshes expired quotes. Set sign_and_send: true to auto-sign and broadcast. |
bridge_status | Track bridge progress. On-chain fallback when API hasn't indexed yet. |
bridge_chains | List supported chains with provider coverage. |
bridge_tokens | Search tokens on a chain. |
Multi-hop & Discovery
| Tool | Description |
|---|
bridge_quote_multi | Multi-hop route resolution when no direct route exists. |
bridgekitty_help | Agent onboarding guide with examples and tool usage. |
xprt_onboard | Guided onboarding flow for first-time users. |
Wallet Tools
| Tool | Description |
|---|
wallet_setup | Create wallets for EVM, Cosmos, Solana from a single mnemonic. |
wallet_import | Import an existing wallet from a mnemonic or private key. |
wallet_status | Show configured wallet addresses and key source. |
wallet_balance | Check balances across all chains with USD prices (CoinGecko). |
XPRT staking & farming has moved to the standalone xprt-farming-toolkit package.
Example: Bridge USDC from Base to Arbitrum
Default (unsigned transactions)
Agent: "Bridge 100 USDC from Base to Arbitrum"
→ bridge_get_quote: Gets quotes from deBridge, Relay, LI.FI, Across
→ Shows: best rate, fees, estimated time, balance check
→ bridge_execute: Builds approval tx + bridge tx
→ Agent signs and sends both transactions
→ bridge_status: Tracks until destination confirmed
With sign_and_send (autonomous signing)
Agent: "Bridge 100 USDC from Base to Arbitrum"
→ bridge_get_quote: Gets quotes from all backends
→ bridge_execute with sign_and_send: true
→ Auto-signs approval tx + bridge tx using local wallet keys
→ Returns tx hash + explorer link
→ bridge_status: Tracks until destination confirmed
Architecture
Agent → MCP Tools → Routing Engine → [deBridge, Relay, LI.FI, Across, Squid]
↓
Quote Cache (60s) + Circuit Breaker
↓
Best Quote → buildTransaction
↓
┌──────────┴──────────┐
↓ ↓
Unsigned TX Signed + Broadcast
(default) (sign_and_send)
- Routing Engine: Parallel quotes from all backends, ranked by output amount
- Circuit Breaker: Auto-skips failing backends, gradual recovery
- Token Registry: 45+ verified tokens with canonical addresses per chain
- Gas Estimator: Chain-aware gas cost estimation with multi-RPC failover
- Balance Checker: Validates token + native balance for fees before execution
- Fee Transparency: Protocol fees (deBridge fixFee, operating expenses) surfaced in every quote
Security
- Exact-amount approvals only (never unlimited)
- Transaction simulation before execution
- Verified token registry prevents address spoofing
- No private keys in MCP protocol — agents sign transactions externally
sign_and_send uses locally-stored keys only (never transmitted over the network)- Circuit breaker prevents cascading failures
- Error messages sanitized (no key/path leakage)
.env file permission checks + overwrite protection
Known Limitations
- Solana → EVM returns a serialized transaction for external signing (no auto-execute)
- Relay status tracking may show "unknown" for completed cross-chain bridges
- Solana SPL tokens not yet shown in
wallet_balance (only native SOL)
- Cosmos → EVM bridging not yet supported (only EVM → Cosmos)
License
MIT