@fidesbuild/mcp-server
FIDES for Claude, and for any other MCP app. You sign a FIDES once, with a budget, the contracts the agent may call and an expiry. Then you ask Claude in plain words, for example "pay 1 USDG to 0x…". Claude plans the actions through FIDES, shows you what is inside the FIDES and what is blocked, and executes only when you say so. Anything outside the FIDES is never sent.
- Funds move from your FIDES Account, never from your wallet.
- The agent key this server makes holds no funds. It can only sign actions inside the FIDES you signed for it.
- Gas is paid by the hosted FIDES relayer, so the agent key needs no ETH.
Set up
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Add FIDES to Claude.
Claude Desktop: download the FIDES extension, double-click it and click Install.
Claude Code, in a terminal, on Windows:
claude mcp add fides -- cmd /c npx -y @fidesbuild/mcp-server@latestOn macOS or Linux:
claude mcp add fides -- npx -y @fidesbuild/mcp-server@latest -
In Claude, say "Set up FIDES". Claude gives you a link to the FIDES app with its agent address filled in.
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Open the link, set the budget, the contracts and the expiry, sign, then create and fund your FIDES Account.
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Ask Claude for what you want. It picks up the signed FIDES by itself; there is nothing to download.
Claude Code and other MCP apps need Node 20.10 or later. Claude Desktop has its own.
Tools
| Tool | What it does |
|---|---|
fides_setup | A link to the FIDES app with this agent filled in |
fides_status | The FIDES: active or not, budget spent and remaining, FIDES Account balance, allowed contracts, expiry, agent address |
fides_plan | Builds transfers and contract calls into one plan, checks each against the FIDES, groups them, simulates. Sends nothing. Calls any verified contract by function name and plain values, encoded from its verified source |
fides_inspect_contract | Reads any contract on the chain and lists what an agent could call, with risky functions flagged |
fides_read_contract | Reads a value from any verified contract by function name, such as a market or a balance. Free |
fides_check_api | Reads a paid API's price without paying, and says whether a FIDES can pay it |
fides_swap | Swaps on Uniswap inside the trading mandate the owner signed |
fides_execute | Executes a plan by its id. Only the actions inside the FIDES are sent |
fides_pay_request | Buys from a paid API over x402: checks the price against the service's cap in the FIDES, pays from the FIDES, returns the response |
fides_receipts | Every transaction executed under the FIDES, with explorer links |
fides_help | What you can do with FIDES, the paid APIs known to work with their prices, and what to try |
fides_use_file | Loads a fides.json file, for a FIDES that was not signed in the app |
The FIDES used is the newest valid one signed for this agent: from the FIDES API, where the app shares a FIDES when it is signed, or from the copy kept in ~/.fides. Each is verified onchain before it is used.
Paid APIs
Claude can buy from APIs that charge per request over x402, from your FIDES. Each paid service is named in the FIDES with a cap; anything not named, or past its cap, is refused before paying. To try it, ask Claude: "Set up FIDES with the fides-demo paid service, up to 0.1 USDG", sign, then "Buy the chain stats from the FIDES demo" (0.01 USDG for Robinhood Chain's latest block, gas price and USDG supply).
Paid APIs known to work, each bought through FIDES with real payments on mainnet:
| Service id | URL | Price |
|---|---|---|
fides-demo | https://api.fidesbuilder.xyz/v1/demo/chain-stats | 0.01 USDG |
spraay | https://gateway.spraay.app/api/v1/models | 0.001 USDG |
madeonsol | https://madeonsol.com/api/x402/rhc/kol/feed?limit=5 | 0.04 USDG |
Any API that charges USDG on Robinhood Chain over x402 (exact, EIP-3009) works the same way. The service id is any name you choose when you sign. Ask Claude "What can you do with FIDES?" to get this list in the chat.
Other MCP apps
Add a server with the command npx and the arguments -y @fidesbuild/mcp-server@latest (on Windows, the command cmd and the arguments /c npx -y @fidesbuild/mcp-server@latest). npx -y @fidesbuild/mcp-server setup makes the agent key and prints the setup link from a terminal.
Settings
All optional, set in the environment of the server.
| Variable | Default |
|---|---|
FIDES_HOME | ~/.fides, where agent.json and the FIDES in use are kept |
FIDES_FILE | ~/.fides/fides.json |
FIDES_RPC | https://rpc.mainnet.chain.robinhood.com |
FIDES_API | https://api.fidesbuilder.xyz: the relayer that pays gas, and where signed FIDES are looked up |
FIDES_APP | https://fidesbuilder.xyz/app, for the setup link |
FIDES_RELAY | Set to self to have the agent key pay gas itself (give it a little ETH) |
FIDES_LOOKUP | Set to off to use only the FIDES kept in FIDES_FILE |
FIDES_AGENT_KEY | Use this private key instead of ~/.fides/agent.json |
The hosted relayer has a daily gas budget shared by everyone. If it runs out, fides_execute says so; use FIDES_RELAY=self or try later.
Docs: fidesbuilder.xyz/docs