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Kura

Kura (蔵 — a storehouse that guards your treasures)

A local EVM wallet for AI agents. On a Mac, when an AI like Claude makes an internet payment (x402), this is the wallet where a human approves it with a password.

  • Not a human wallet (like MetaMask) — it's for AI agents

  • Not a cloud SaaS — it runs locally only. Keys never leave this computer.

  • AI requests a payment → a human approves with a password → it executes

  • The chain is Base (Ethereum L2, near-zero fees). Default is the testnet (Base Sepolia)


At a glance

[ AI 앱 (Claude Code / 데스크톱) ]
        │  MCP로 "결제해줘" 요청
        ▼
[ Kura 데스크톱 앱 ]  ← 승인 팝업 → 사람이 비밀번호 입력
        │  서명 (키는 이 앱 안에서만)
        ▼
[ Base 체인 / x402 페이실리테이터 ]  ← 실제 결제

The password is only ever entered in the Kura app's input field. It never goes into chat windows, MCP, or config files.


Related MCP server: cardzero-mcp

Installation

Apple Silicon Mac (macOS 11 or later)

(A) Homebrew

brew install --cask dinggi5/tap/kura

(B) Download the DMG directly

Download Kura_<version>_aarch64.dmg from Releases, open it, and drag Kura into the Applications folder.

Since this is an app you're entrusting with your keys, I've written down the exact commands for verifying that the app you received is really the one I built in SECURITY.md.

(C) Build from source

Prerequisites: Rust, Node.js (20.19+ or 22.12+ — required by Vite 7), macOS.

git clone https://github.com/dinggi5/kura.git
cd kura
git checkout v0.1.1   # 배포본과 같은 소스. 빼면 개발 중인 최신 코드가 받아져요
npm ci                # package-lock.json 그대로 설치 (install 은 버전이 올라갈 수 있어요)

# 개발 모드로 바로 실행
npm run tauri dev

# 앱으로 빌드해 /Applications에 설치
npm run tauri build -- --bundles app --no-sign
ditto src-tauri/target/release/bundle/macos/Kura.app /Applications/Kura.app
open /Applications/Kura.app

Updates

The app updates itself.
Go to Settings → About to check the version and changelog, then click Install now and restart.

  • Only the check is automatic — installation always requires you to click it.

  • Downloaded files are installed only after their signature is verified (signature verification cannot be disabled). Details are in the "Updates" section of SECURITY.md.

  • If you don't want the automatic update-check traffic, turn off Settings → About → Check on startup.

Uninstalling

⚠️ Uninstalling the app does not delete your wallet. Keys, settings, and transaction history live in ~/.jigap outside the app, so removing just the app leaves them intact — I did this on purpose so you don't accidentally lose your assets (even brew uninstall --zap won't remove them).

# 앱만 제거 (지갑은 남음 — 나중에 다시 설치하면 그대로 이어서 써요)
brew uninstall --cask dinggi5/tap/kura   # 또는 /Applications/Kura.app 을 휴지통으로

To completely erase the wallet too on this Mac, follow this order:

  1. First make sure you have the 12-word recovery phrase in hand. You can view it again via the key button in the app's header.

  2. If there's a balance left, move it to another wallet.

  3. Quit Kura completely (right-click the menu bar icon → Quit). If it's running, it writes a state file to ~/.jigap every few seconds, so a deleted folder will reappear right away.

  4. Also quit any AI tools (like Claude Code) that have the Kura MCP attached.

  5. If you had auto-start enabled, turn it off or run rm ~/Library/LaunchAgents/Kura.plist (this file remains if you delete the app via Trash. If you uninstall with brew uninstall --cask, it goes away with it).

  6. Then run rm -rf ~/.jigap

Running that final rm -rf ~/.jigap without the 12 words means no one can ever recover that wallet's assets.


First run

Kura lives in the menu bar. When you launch it, a storehouse icon (◻︎) appears in the menu bar at the top of your screen, and the window only drops down when you click that icon. Clicking elsewhere closes it, and the app stays in the background waiting for AI payment requests. To quit completely, right-click the icon → Quit. (On first launch when no wallet exists yet, the window opens by itself.)

  1. Create a wallet — set a password (8+ characters) that you'll enter for every transfer. Your key is encrypted and stored with this password (~/.jigap/wallet.enc).

  2. Back up the seed — 12 words are shown. This is the real proof of ownership of your assets, so write them down on paper or in a password manager. Even if you forget your password, the 12 words alone can recover it: quit the app, first make sure you have the 12 words in hand, then delete ~/.jigap/wallet.enc and relaunch the app — you can restore it via Import on the first screen (you can also put them into any other standard BIP-39 wallet). However, deleting this file without the 12 words means losing your assets forever.

  3. Welcome tour — walks you through funding, AI connection, and safety features. You can revisit it anytime from the ⓘ Help in the header.


Funding (USDC)

To make payments, your wallet needs USDC (digital dollars).

  • Tap Receive in the app to see your address and QR code.

  • When sending from an exchange or another wallet, be sure to select the Base network. Sending on another network will lose your funds.

  • On the testnet (default), it's not real money. Use the Faucet button on the receive screen to get free test coins and practice.

  • ETH is optional — for x402 payments, the facilitator pays the fee, so you can have 0 ETH. You only need a little ETH for gas when sending directly via the app's Send (Base fees are around a cent). Funding with USDC alone is enough.


Connecting AI (Claude)

Register the Kura server in your AI app's MCP settings to connect. Once connected, a "Claude connected" badge appears on the main screen. Since 0.1.2, the MCP server is built into the app, so you can connect without cloning the source or installing Rust.

The easiest way — the "AI Connect" screen in the app

Click the "AI not connected" badge at the top of the main screen to open the connection screen.

  • Claude Desktop — click the "Connect" button and an extension install window appears in Claude. Just click 'Install' and you're done.

  • Claude Code — registered with one click (the app runs claude mcp add for you). From the next claude launch, it's connected from any folder.

Below is how to do the same thing by hand.

Claude Desktop — one extension file is all you need

Download kura-<version>.mcpb from the releases page and double-click it — Claude Desktop will ask to install it. (Or go to Claude Settings → Extensions → Choose file.)

The extension contains no executable — it only has a launcher that verifies the signature of the signed and notarized MCP server inside the installed Kura.app and then runs it. So you need to install the Kura app first.

Claude Code · other MCP apps

Register the in-app binary with its absolute path:

claude mcp add --scope user kura -- /Applications/Kura.app/Contents/MacOS/kura-mcp

(--scope user is the option that makes it available everywhere, not just "this folder". If you only want it in one project, you can omit it.)

For other MCP apps, write it in the settings like this:

{
  "mcpServers": {
    "kura": {
      "command": "/Applications/Kura.app/Contents/MacOS/kura-mcp"
    }
  }
}

If you're developing from source

The repo root already has .mcp.json. Running claude in this folder picks it up automatically (the first time it asks whether to use the server — approve it). This path is for development, rebuilding with cargo run every time — if you're using an installed build, registering the app path above is the right approach.

Tools the AI can use: get_wallet_status · get_balances · get_history (read-only) · request_payment (payment request → approval popup in the app) · x402_fetch (calls a URL that requires 402 payment).

If you change the MCP tools, restart the AI app for it to take effect (the server is loaded once at session start).


How a payment flows

  1. The AI requests a payment.

  2. The Kura window appears showing how much, to where (it pops up automatically even if the window was hidden).

  3. Enter the password and approve.

  4. The payment executes and the result goes back to the AI. If you don't approve within 5 minutes, it's automatically rejected.


Security model

  • Password approval — by default, every payment requires password approval (if autonomous payments are enabled, exceptions apply only under the conditions below). Keys are stored encrypted (Argon2id + AES-256-GCM) and are only decrypted at payment time, then wiped immediately (if an autonomous payment session is enabled, they're kept in memory only while unlocked).

  • Limits — set how much can be sent per transaction / per day in settings (default: 5 USDC single, 20 USDC daily). Anything over is blocked.

  • Emergency lock — turning on the shield button in the header immediately blocks all transfers.

  • Trusted addresses · autonomous payments — for automatic approval without a password, session unlock + small limits + trusted address must all be satisfied. Otherwise, a password is always required.

  • Transaction history — records all outgoing transfers, blocked attempts, and signatures.

  • Local-first — keys (~/.jigap/) live outside the repo and never get committed to git.

  • No analytics, no font CDN — the app connects to the internet on its own for only three things: ①the RPC server used for balance lookups and transfers ②x402 addresses requested by the AI ③update checks (GitHub). Usage data is never sent anywhere, and fonts are bundled in the app, so the UI renders fine offline too.

  • Update checks can be disabled — on launch it asks GitHub whether a new version exists (your IP and current version are logged there). Turning off Settings → About → Check on startup removes even this traffic. Whether the check is on or off, installation only proceeds when you click it — nothing ever changes silently.


For developers

You can also drive the same wallet from the CLI kura (it shares the MCP server and core logic). It's already inside the installed app, so one line on your PATH and you're set:

sudo mkdir -p /usr/local/bin
sudo ln -sf /Applications/Kura.app/Contents/MacOS/kura-cli /usr/local/bin/kura
kura status

To run from source:

cargo run --manifest-path ./kura-mcp/Cargo.toml --bin kura -- status
cargo run --manifest-path ./kura-mcp/Cargo.toml --bin kura -- balance
cargo run --manifest-path ./kura-mcp/Cargo.toml --bin kura -- history --limit 10
cargo run --manifest-path ./kura-mcp/Cargo.toml --bin kura -- pay <주소> <금액> --token usdc
cargo run --manifest-path ./kura-mcp/Cargo.toml --bin kura -- fetch <URL>

pay/fetch never take a password via the CLI — the Kura app must be running, and a human enters the password in the approval popup.

Tests:

(cd src-tauri && cargo test)        # 백엔드(지갑·암호화·한도·송금)
(cd kura-mcp && cargo test)         # MCP/CLI 어댑터
npx tsc --noEmit && npx vite build  # 프론트

The procedure for producing a release build (signed, notarized DMG) is in docs/RELEASE.md. It needs an Apple Developer account and a one-time setup, and after that it's one line:

./scripts/release.sh

Tech stack

Desktop

Tauri (Rust + web frontend)

Frontend

React + Tailwind CSS, Framer Motion, Lucide, Pretendard

Chain

Base / alloy-rs

Payments

x402 (EIP-3009 off-chain signatures)

AI connect

MCP server (rmcp)

Structure: [Rust core (src-tauri)] ← MCP / CLI adapters (kura-mcp). Only the GUI process has key access (signing) — that's the last line of defense.


License · status

MIT license — since this is code that handles keys and money, I believe it should be something you can read, verify, and modify yourself.

If you find a vulnerability, please report it through the private channel in SECURITY.md before filing an issue. The same document also lists what Kura cannot protect against.

The bundled Pretendard font is under the SIL Open Font License 1.1 (full text).

The number one user is myself — a wallet for Korean developers and creators on Apple Silicon Macs who pay with local LLMs/Claude. It's still an early 0.1.x version, so I recommend learning on the default testnet first and only putting what you can afford to lose on mainnet.

Available Tools

7 tools
get_balancesBalancesA
Read-only

Reads the active account's USDC (for payments) and gas-token balances on the active network (Base mainnet, Arc mainnet, Base Sepolia, or Arc testnet, per the user's setting). The eth field is the gas balance and is ABSENT on chains where gas is paid in USDC itself (Arc) — there the USDC balance already covers gas, so never add the two together. Errors if there is no wallet.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

TDQS

A4.1/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description goes further by disclosing the no-wallet error case and a critical cross-field caveat (the `eth` gas field is absent on Arc and must never be added to the USDC balance). It does not cover rate limits or refresh/freshness behavior, so it stops short of a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the core read action, followed by the field caveat and the error case. The parenthetical enumeration of the four networks is slightly heavy but genuinely useful since it defines the valid scope; nearly every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no parameters and no output schema, the description carries the burden of explaining the return shape, and it does so reasonably: it names the two balance types, flags the missing `eth` field per chain, and states the error case. Minor gap is freshness/caching and what happens across multiple networks at once.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4. The description's field-level discussion (USDC vs `eth` gas balance and their relationship on Arc) concerns returned values rather than inputs, but it does add interpretive value that the empty schema cannot.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Reads') and resource (USDC and gas-token balances) for the active account, and pins the scope to the active network with named chains. An agent can immediately distinguish this from get_wallet_status or get_history without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by the purpose but never stated as when-to-use or when-not-to-use, and no sibling tool is named as an alternative. The only routing signal is the failure condition ('Errors if there is no wallet'), which is a precondition rather than guidance on choosing this tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

get_historyHistoryA
Read-only

Returns the active account's recent transaction attempts, newest first. status is one of sent, blocked, failed, signed (x402 signed, awaiting settlement), settled (x402 settled, settle_tx is the settlement tx), settle_failed, unknown (a signed transaction was submitted but the wallet couldn't confirm the chain received it — detail is its tx hash; it may have gone through, so never resend on the strength of this entry alone; the wallet app later rechecks it on-chain and turns it into sent or reverted), reverted (mined but reverted on-chain — no money moved, only gas), expired (an x402 signature that was never used before it expired — no money moved), or received (money that came in — to is the sender, detail the tx hash; both are empty for ETH a contract sent; found on-chain by the wallet app while it runs, back to 90 days). Use limit to cap how many come back (default 20).

ParametersJSON Schema
NameRequiredDescriptionDefault
limitNoHow many recent entries to return (default 20, max 200).

TDQS

A4.2/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only declare readOnlyHint and openWorldHint; the description carries substantial extra behavior: per-status meaning, which statuses mean no money moved (reverted, expired), that 'unknown' may have gone through and the wallet rechecks it on-chain, that 'received' comes from an app-driven on-chain scan back to 90 days. This is exactly the context annotations cannot supply.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The core purpose is front-loaded and every clause carries information — the status enumeration is necessary because there is no output schema. It loses a point because the status glossary is delivered as one very dense run-on sentence rather than a scannable list.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema and only one optional parameter, the description fully covers what the agent needs: return ordering, default limit, and the complete semantics of every status value including financial and safety implications. Nothing material is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% for the single 'limit' parameter, so the schema already documents default 20 and max 200; the description only restates the default. Baseline 3 applies since the schema does the heavy lifting and the description adds no new parameter syntax.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource — 'Returns the active account's recent transaction attempts, newest first' — including scope (active account) and ordering. The resource is unmistakably distinct from siblings like get_balances and get_wallet_status, so an agent can route without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied by the resource and by the embedded warning 'never resend on the strength of this entry alone', which quietly steers the agent away from acting on 'unknown' entries via x402_resubmit. However, it never explicitly says when to call this versus alternatives, nor states prerequisites or exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

get_wallet_statusWallet statusA
Read-only

Returns the wallet's state and address. state is encrypted (normal), legacy, or none. address is the ACTIVE account's address; accounts lists every account in the wallet (index, address, label) and account is the active index. Balances, history, and payment requests all use the active account, and only the user can switch accounts, in the wallet app. No password needed — read only.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

TDQS

A4.4/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description goes well beyond them: it enumerates the state values (encrypted/legacy/none), clarifies that address is the ACTIVE account while accounts lists all accounts, and discloses that only the user can switch accounts in the wallet app. It also reassures no password is needed, which is actionable auth context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core purpose, then structured field-by-field. Every sentence carries information, though the trailing 'No password needed — read only' partially restates the readOnlyHint annotation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With zero parameters, no output schema, and annotations covering safety, the description supplies exactly the missing pieces: what fields come back, what the state values mean, and how the active-account concept relates to sibling tools. Nothing an agent needs to call this correctly is absent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes zero parameters, so the baseline is 4. The description additionally documents the shape of the returned object (index, address, label, active index), which is useful given no output schema exists, though these are return values rather than input semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Returns the wallet's state and address') and enumerates the exact fields returned (state, address, accounts, account). The sibling set (get_balances, get_history, request_payment) is clearly distinct, and the description anchors its scope to the active account rather than those other resources.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is implied rather than stated: it explains that balances, history, and payment requests all key off the active account, which tells the agent why it might call this first, but it never explicitly says when to use this tool versus get_balances/get_history, nor names an alternative.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

lookup_agentLook up an agent (ERC-8004)A
Read-only

Reads an agent's ERC-8004 record from the registry on the active network (read-only, on-chain only — the wallet never fetches the agent's website). Give it agent_id, the agent's number in the Identity Registry. Returns: registered, owner, wallet (the registered agentWallet), token_uri and the uri_domain read from it, declared_name (what the record calls itself), and feedback_clients (how many addresses left feedback). Pass pay_to and/or resource to also get a comparison: whether the address equals the registered wallet and whether the resource's domain equals the domain listed on-chain. IMPORTANT: registration is permissionless — anyone can register any name, domain, or wallet, and anyone can leave feedback. Being registered is NOT proof of safety. Only a mismatch is a strong signal, and only when the agent number came from a source you trust (the service's own docs), not from the payment response itself.

ParametersJSON Schema
NameRequiredDescriptionDefault
pay_toNoOptional: an address to compare against the agent's registered wallet.
agent_idYesThe agent's ERC-8004 number (agentId — the Identity Registry NFT token id).
resourceNoOptional: a resource URL whose domain is compared with the domain listed on-chain.

TDQS

A4.6/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, and the description goes well beyond them: it discloses that nothing is fetched off-chain, that registration is permissionless, and that being registered is not evidence of safety. This is exactly the kind of adversarial-context caveat an agent needs before treating the result as a trust signal.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core action, then the return fields, then the comparison behavior, then the safety caveat. The enumerated return list is long but every item earns its place given there is no output schema. Slightly dense, but no filler sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description fully enumerates the returned fields (registered, owner, wallet, token_uri, uri_domain, declared_name, feedback_clients) plus the conditional comparison outputs. For a read-only lookup with three parameters, nothing an agent needs to call or interpret it is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds real semantics: agent_id is the number in the Identity Registry, and pay_to/resource exist specifically to produce address and domain comparisons. That comparison behavior is not derivable from the terse schema property descriptions alone.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: reads an agent's ERC-8004 record from the on-chain registry on the active network. It immediately scopes what the tool does not reach ("the wallet never fetches the agent's website"), which separates it cleanly from the payment/wallet siblings. An agent can tell what this returns without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete invocation guidance (supply agent_id; optionally pass pay_to and/or resource to trigger a comparison) and states the condition under which the result is trustworthy (mismatch only matters when the agent number came from a source you trust). No sibling alternative is named, but the siblings are unrelated domains so the omission is minor. Clear context without explicit when-not-to-call routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

request_paymentRequest a paymentA
Destructive

Asks the user to make a payment. The wallet app opens an approval window, and the payment is only sent once the user approves it with their password (it waits up to 5 minutes). The one exception is autopay, which the user turns on themselves — only then can a payment be approved automatically, and only within an unlocked session, a small limit, and a trusted address. Arguments: to (recipient address), amount (decimal string), token (USDC by default, or ETH), memo (what the payment is for — the user reads it to decide, so always fill it in), and optionally agent_id (the recipient's ERC-8004 number, if a service told you one — the wallet then shows the user whether the address matches that agent's registered wallet). Per-payment and daily limits and the emergency lock are enforced by the app. Never send a password as an argument — the user types it in the app. Returns: status, tx_hash, detail, and an explorer link. status is approved (the chain accepted the transfer), rejected or failed (nothing was sent — safe to ask again), or unknown: the user approved but the wallet couldn't confirm whether the transfer reached the chain (tx_hash is set when known). unknown means it MAY have been sent — never ask again on your own; tell the user and have them check the history or the tx.

ParametersJSON Schema
NameRequiredDescriptionDefault
toYesRecipient address (42 characters, starting with 0x).
memoNoWhat the payment is for — the user reads this in the approval window, so fill it in.
tokenNoToken: "USDC" (default) or "ETH".
amountYesAmount as a decimal string, for example "1.5".
agent_idNoOptional: the recipient's ERC-8004 agent number, if you know it from the service's own documentation or agent card. The wallet reads that agent's on-chain record and tells the user whether the address you are paying is the one registered for that agent. A mismatch is the useful part — a match is not proof of anything, since anyone can register. Leave it out if you don't know it; a wrong number just produces a "no such agent" note.

TDQS

A4.8/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and idempotentHint=false, but the description adds far more: a 5-minute approval timeout, password-entry-only-in-app, app-enforced per-payment/daily limits and emergency lock, autopay preconditions (unlocked session, small limit, trusted address), and the semantics of approved/rejected/failed/unknown including the no-retry rule on unknown. That is exactly the behavioral disclosure a payment tool needs.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with purpose, then arguments, then return semantics in a logical order. It is long, but the length is justified by the absence of an output schema and the high stakes of an irreversible transfer; each section earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description fully documents the return contract (status, tx_hash, detail, explorer link) and the three status branches, plus the critical unknown-may-have-been-sent caveat. Nothing needed to invoke or handle the result is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds operative meaning beyond the schema: 'USDC by default', the instruction to always fill in memo because the user reads it, and a caution that agent_id mismatch is the useful signal while a match proves nothing. It largely restates the schema fields, but the added rationale has real value.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Asks the user to make a payment') and immediately distinguishes it from read-only siblings like get_balances/get_history by describing the approval-window flow. An agent can tell this is the mutating spend path without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit when-to-use and when-not-to-act guidance: the approval window is the normal path, autopay is the only auto-approval exception and only under user-enabled conditions, and on 'unknown' the agent must never retry on its own but hand off to the user. This is actionable routing logic, not vague context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

x402_fetchFetch a paid URL (x402)A
Destructive

Calls an x402 paid API or URL. It sends the request first — GET by default, or the given method (POST, PUT, PATCH, DELETE) with optional headers and a JSON object body; if the server answers 402 Payment Required, it asks the user to approve the required payment (exact scheme, the active network, that chain's USDC) in the wallet app, then sends the SAME request (same method, headers and body) again with the payment header and returns the content. If no payment is required (no 402), it just returns the response. Redirects are not followed once a payment header is attached (nor at all when method, headers or body are given) — a redirect comes back as an error with the new address. Text and JSON come back in body. Binary responses (images, PDF, audio) are saved to a file whose path is in saved_file (with content_type); a PNG/JPEG/GIF/WebP image up to 3 MB is also attached as an image. Text longer than 100,000 characters is cut in body and kept whole in saved_file. If saving takes too long (macOS asking for Downloads access), the result comes back first and saving_file names where the file will appear. Settlement takes one of two shapes, chosen by the server's requirement: a facilitator settles the signed EIP-3009 authorization (no gas from this wallet), or — where gas is paid in USDC itself and the server asks for eip3009-client-broadcast — the wallet broadcasts the transfer itself, so the price AND its gas leave this balance. Approval works exactly as in request_payment (password by default; automatic only when the user has turned autopay on), and the app enforces per-payment and daily limits and the emergency lock. Never send a password as an argument. Arguments: url (required), method, headers, body (JSON object), memo (what the payment is for — the user reads it to decide), agent_id. Returns: payment, paid, status, http_status, body, and amount/pay_to/settlement when paid; on a chain where the wallet broadcasts the payment itself, tx and explorer point at that transaction (both are empty on the facilitator-settled path, where settlement_tx/settlement_explorer carry the transaction the seller reports in its receipt — the seller's word, not checked on-chain by the wallet). IMPORTANT — decide on payment, which says where the money is: "none" = nothing was paid, trying again is safe (declined, no 402, or "reverted": the chain rejected the transfer and only gas was spent); "confirmed" = the money left the wallet; "unknown" = it MAY have left (status pending/unknown, or settlement_failed on the facilitator path, where the server's refusal doesn't prove the facilitator didn't settle). For confirmed and unknown without content, asking again can pay a second time — stop and tell the user, showing the tx (when a tx came back without content, x402_resubmit re-sends its proof without paying again). paid is kept for older callers and is simply payment != "none". Read notice when present, and never retry on an HTTP status alone: after the money moved the server may answer with a fresh 402 challenge that reads as if the payment never happened.

ParametersJSON Schema
NameRequiredDescriptionDefault
urlYesURL of the paid resource to fetch (http/https).
bodyNoJSON object sent as the request body (not allowed with GET). Content-Type defaults to application/json. The paid retry sends exactly the same body.
memoNoWhat the payment is for — the user reads this in the approval window, so fill it in.
methodNoHTTP method: GET (default), POST, PUT, PATCH or DELETE. Many paid APIs (search, image generation) take POST with a JSON body. The paid retry uses the same method.
headersNoExtra request headers as a JSON object of name → value. Payment headers, Host, Content-Length and connection headers are set by the wallet and are refused here. The paid retry sends the same headers.
agent_idNoOptional: the seller's ERC-8004 agent number, if you know it from the service's own documentation or agent card. The wallet then reads that agent's on-chain record and shows the user whether the payment address and the resource domain match what is registered. Leave it out if you don't know it — a wrong number just produces a "no such agent" note.

TDQS

A4.6/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only say destructive/openWorld/non-idempotent, while the description discloses far more: the retry-safety semantics of the `payment` field ('none'/'confirmed'/'unknown'), the double-payment hazard, facilitator vs eip3009-client-broadcast gas behavior, redirect handling under a payment header, the 100k truncation and saved_file behavior, and the warning never to retry on HTTP status alone. This is exactly the value-beyond-annotations the dimension rewards, and the destructiveHint is consistent with money leaving the wallet.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The basic request flow is front-loaded before the settlement and retry-safety detail, and nearly every sentence carries operational or safety weight. It is nevertheless very long for a single tool, with some density that could be tightened, so it stops short of a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description carries the full burden of explaining returns — and it does: payment/paid/status/http_status/body/amount/pay_to/settlement, tx/explorer vs settlement_tx, and notice. For a 6-param destructive payment tool, an agent has everything needed to call it and interpret the result safely.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: it explains memo is what the user reads to decide, agent_id drives an on-chain ERC-8004 verification note, and it warns never to pass a password as an argument. These are semantic additions beyond the schema text.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The opening sentence gives a specific verb and resource ('Calls an x402 paid API or URL') and the whole description keeps the scope tight around paid HTTP fetching. It distinguishes itself from request_payment by reference ('Approval works exactly as in request_payment') and from x402_resubmit by naming it as the no-pay-again path. An agent can separate it from every sibling without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It clearly states the triggering condition (server answers 402 → user approval → same request resent), when the tool is a plain fetch (no 402), and routes to x402_resubmit when a tx came back without content. It does not give an explicit 'prefer X over request_payment when...' decision rule, but the surrounding context is strong enough to infer usage.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

x402_resubmitResubmit an x402 payment proofA
Idempotent

Resubmits the on-chain proof of an x402 payment this wallet already broadcast itself, to get the content it paid for. Use it when x402_fetch returned a tx without content (status pending, unknown or undelivered, or settlement_failed with a tx). No new money moves and no approval is asked: the wallet re-sends the same proof (the tx plus the saved challenge values) to the same URL. It first checks the tx on-chain — if it isn't mined yet you get status pending (wait and call again), if it reverted you get reverted (payment none: nothing was paid, so paying again is a new decision). Sellers keep proofs acceptable only for a while (the reference server: 10 minutes), so a late resubmit can be refused — that is settlement_failed with a notice; do not pay again then, tell the user and show the tx. Proofs are kept for 7 days. Returns the same shape as x402_fetch.

ParametersJSON Schema
NameRequiredDescriptionDefault
txYesThe `tx` that x402_fetch returned for a payment the wallet broadcast itself (status pending, unknown or undelivered, or settlement_failed with a tx).

TDQS

A4.9/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Far exceeds the annotations: it states no new money moves and no approval is requested, describes the on-chain pre-check and each resulting status (pending, reverted with payment none), and discloses the seller acceptance window (~10 minutes on the reference server) and 7-day proof retention. The idempotent/read-only nature is confirmed in prose rather than left to the hints alone.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose is front-loaded in the first clause, followed by the usage trigger and then the behavioral detail. The length is justified by the number of distinct outcomes (pending, reverted, refused) that the agent must handle correctly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Although there is no output schema, the description states the return shape matches x402_fetch and enumerates every status the caller may encounter along with the correct reaction to each. Nothing an agent needs to invoke or interpret this tool is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: the tx must be one the wallet broadcast itself and is re-sent together with the saved challenge values to the same URL. That provenance and pairing context goes beyond the schema's bare field description.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (resubmits the on-chain proof of an x402 payment this wallet already broadcast) plus the goal (to get the content it paid for). It also distinguishes itself from the sibling x402_fetch by explicitly framing itself as the follow-up for a tx that came back without content.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly names the trigger condition: 'Use it when x402_fetch returned a `tx` without content (status pending, unknown or undelivered, or settlement_failed with a tx).' It also names the alternative (x402_fetch) and warns against paying again in the settlement_failed/refused cases.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 1 tool updatev0.5.0
    • Changedx402_fetch3 fields changed
      • addedInput schema / properties / body
        Added value: +{
        +  "additionalProperties": true,
        +  "description": "JSON object sent as the request body (not allowed with GET). Content-Type defaults to\napplication/json. The paid retry sends exactly the same body.",
        +  "type": "object"
        +}
      • addedInput schema / properties / headers
        Added value: +{
        +  "additionalProperties": {
        +    "type": "string"
        +  },
        +  "description": "Extra request headers as a JSON object of name → value. Payment headers, Host,\nContent-Length and connection headers are set by the wallet and are refused here.\nThe paid retry sends the same headers.",
        +  "type": "object"
        +}
      • addedInput schema / properties / method
        Added value: +{
        +  "description": "HTTP method: GET (default), POST, PUT, PATCH or DELETE. Many paid APIs (search, image\ngeneration) take POST with a JSON body. The paid retry uses the same method.",
        +  "type": "string"
        +}
  2. 1 tool updatev0.4.3
    • Addedx402_resubmit
  3. 4 tool updatesv0.4.1
    • Changedget_history2 fields changed
      • removedInput schema / properties / limit / default
        Removed value: -null
      • removedInput schema / properties / limit / nullable
        Removed value: -true
    • Changedlookup_agent4 fields changed
      • removedInput schema / properties / pay_to / default
        Removed value: -null
      • removedInput schema / properties / pay_to / nullable
        Removed value: -true
      • removedInput schema / properties / resource / default
        Removed value: -null
      • removedInput schema / properties / resource / nullable
        Removed value: -true
    • Changedrequest_payment6 fields changed
      • removedInput schema / properties / agent_id / default
        Removed value: -null
      • removedInput schema / properties / agent_id / nullable
        Removed value: -true
      • removedInput schema / properties / memo / default
        Removed value: -null
      • removedInput schema / properties / memo / nullable
        Removed value: -true
      • removedInput schema / properties / token / default
        Removed value: -null
      • removedInput schema / properties / token / nullable
        Removed value: -true
    • Changedx402_fetch4 fields changed
      • removedInput schema / properties / agent_id / default
        Removed value: -null
      • removedInput schema / properties / agent_id / nullable
        Removed value: -true
      • removedInput schema / properties / memo / default
        Removed value: -null
      • removedInput schema / properties / memo / nullable
        Removed value: -true
  4. 1 tool updatev0.4.0
    • Changedrequest_payment1 field changed
      • addedInput schema / properties / agent_id
        Added value: +{
        +  "default": null,
        +  "description": "Optional: the recipient's ERC-8004 agent number, if you know it from the service's own\ndocumentation or agent card. The wallet reads that agent's on-chain record and tells the\nuser whether the address you are paying is the one registered for that agent. A mismatch\nis the useful part — a match is not proof of anything, since anyone can register.\nLeave it out if you don't know it; a wrong number just produces a \"no such agent\" note.",
        +  "format": "uint64",
        +  "minimum": 0,
        +  "nullable": true,
        +  "type": "integer"
        +}
  5. 2 tool updatesv0.3.0
    • Addedlookup_agent
    • Changedx402_fetch1 field changed
      • addedInput schema / properties / agent_id
        Added value: +{
        +  "default": null,
        +  "description": "Optional: the seller's ERC-8004 agent number, if you know it from the service's own\ndocumentation or agent card. The wallet then reads that agent's on-chain record and shows\nthe user whether the payment address and the resource domain match what is registered.\nLeave it out if you don't know it — a wrong number just produces a \"no such agent\" note.",
        +  "format": "uint64",
        +  "minimum": 0,
        +  "nullable": true,
        +  "type": "integer"
        +}
  6. 5 tool updatesv0.2.0
    • First observedget_balances
    • First observedget_history
    • First observedget_wallet_status
    • First observedrequest_payment
    • First observedx402_fetch

TDQS

A4.3/5.0

Scored across 7 tools

Disambiguation4/5

Most tools are clearly distinct (request_payment, get_wallet_status, get_balances, get_history, lookup_agent). The only partial overlaps are request_payment vs x402_fetch (both trigger payments) and x402_fetch vs x402_resubmit, though the descriptions clearly delineate direct transfer vs paid API call vs proof resubmission without new money.

Naming Consistency4/5

Consistent snake_case verb_noun pattern (request_payment, get_wallet_status, get_balances, get_history, lookup_agent), with x402_fetch and x402_resubmit using a coherent namespace prefix. Minor deviation from pure verb_noun but overall predictable.

Tool Count5/5

7 tools is well-scoped for a wallet/payment server, with each tool earning its place. No redundant or filler tools.

Completeness4/5

Covers the core wallet lifecycle: payments, status/accounts, balances, history, x402 paid fetches with resubmission, and agent registry lookup. Minor gaps like account-switching (explicitly user-only) or explicit cancellation are reasonable omissions, but no major workflow dead ends.

Maintenance

ActivityActive
ResponsivenessUnresponsive

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