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BC x402-client

Make and receive USDC payments over HTTP using the x402 protocol (Coinbase). The Stripe for agents — pay for services, sell your own, check balances. Works on Base network (mainnet + testnet).

modbender/skill-library-mcp Agent Skills author: modbender MIT 11 files · 1 script body ≈ 1 253 tokens Open the sourcegithub.com↗ analyzed 2 d ago

Make and receive USDC payments over HTTP using the x402 protocol (Coinbase).

As a process C 53/100 · Has gaps — weak spots: result and completion, when it triggers, inputs and preconditions

GeneratorStripeAI and agentstype and topics are labelled automatically from the skill text
Runs in: OpenClaw Claude / Claude Code ChatGPT / Codex Gemini CLI Cursor GitHub Copilot / VS Code Qwen Code Kimi Code CLI Z.ai (GLM) DeepSeek (Deep Code) Mistral Vibe LangChain (deepagents) Goose OpenCode
JSON
Technical rating
B
79/100
safety, quality, tests
Safety 60%
82
Quality 40%
75
Run on models
none yet
Process rating
C
53/100
Has gaps
Result and completion w 14
0
Inputs and preconditions w 11
0
Failures and branches w 10
0
the three weakest of ten parameters · all ten

What is at stake

Medium-severity findings: the skill is probably honest, but read what alarmed the scanner.

Risky intent medium severity

Below is the worst case for this category. The finding here is medium: the guard saw a sign, not a proof.

If you install

The purpose itself is risky: wallets, browser password stores, offensive security. Even an honest implementation gives the agent access to things that cost money.

For the author

Explain in the description why the access is needed and how it is limited; add tests that show refusals on dangerous requests.

How to improve

  1. Say in the description WHEN to use the skill ("use when…", example requests): that is the agent's main cue.
For the model run — optional
  • Your own cases (evals/evals.json, 4–6 real requests with expected answers): the full check would then run those instead of a model-drafted suite.
  • A spec.yaml with trigger phrases and assertions — a behaviour contract for CI; `skilltest init` writes a template.

Guard findings · 10

✓ No critical or high findings

Medium and low: 10
  • medium Risky intent intent-wallet-secrets lib/client.js:62
    Handles crypto-wallet secrets (seed / mnemonic / private key) — a classic stealer target
    // Create signer from wallet private key
  • medium Risky intent intent-wallet-secrets scripts/pay-request.js:81
    Handles crypto-wallet secrets (seed / mnemonic / private key) — a classic stealer target
    // Create signer from wallet private key
  • low Secrets in code secret-high-entropy-token lib/client.js:126
    High-entropy token-like string (may be an id, hash or a credential) (detector / deny-list definition)
    "base": { rpc: "https://mainnet.base.org", contract: "0x83…913" },
    detector
  • low Secrets in code secret-high-entropy-token lib/client.js:127
    High-entropy token-like string (may be an id, hash or a credential) (detector / deny-list definition)
    "base-sepolia": { rpc: "https://sepolia.base.org", contract: "0x03…F7e" },
    detector
  • low Secrets in code secret-high-entropy-token lib/server.js:28
    High-entropy token-like string (may be an id, hash or a credential) (quoted — discussed, not commanded)
    "eip155:8453": "0x83…913",     // Base mainnet
    quoted
  • low Secrets in code secret-high-entropy-token lib/server.js:29
    High-entropy token-like string (may be an id, hash or a credential) (quoted — discussed, not commanded)
    "eip1…532": "0x03…F7e",    // Base Sepolia
    quoted
  • low Secrets in code secret-high-entropy-token scripts/test-e2e.js:68
    High-entropy token-like string (may be an id, hash or a credential) (test fixture / example file; quoted — discussed, not commanded)
    asset: "0x03…F7e", // USDC on Base Sepolia
    fixturequoted
  • low Secrets in code secret-high-entropy-token scripts/test-e2e.js:114
    High-entropy token-like string (may be an id, hash or a credential) (test fixture / example file; quoted — discussed, not commanded)
    asset: "0x03…F7e",
    fixturequoted
  • low Secrets in code secret-high-entropy-token scripts/wallet-balance.js:17
    High-entropy token-like string (may be an id, hash or a credential) (detector / deny-list definition)
    contract: "0x83…913",
    detector
  • low Secrets in code secret-high-entropy-token scripts/wallet-balance.js:22
    High-entropy token-like string (may be an id, hash or a credential) (detector / deny-list definition)
    contract: "0x03…F7e",
    detector

Files scanned: 11. Evidence is masked. Grey chips explain why severity was lowered.

Against the Agent Skills spec

  • warning description-no-when description does not say WHEN to use the skill (no "use when")

Process rating: all ten parameters 53/100

  • 0Result and completion. Does not say what the result is
  • 0Inputs and preconditions. Does not say what the process needs to start
  • 0Failures and branches. Linear process with no failure handling
  • 0Progress reporting. Says nothing while it works
  • 20When it triggers. No condition that starts the skill
  • 100Tools and files. No external tools needed
  • 100Steps. 16 steps
  • 100Consistency. Name and required fields are in place
  • 100Execution cost. Instruction body is 1253 tokens
  • 100Running it twice. Mutating operations check current state
  • medium Safety rules and hard prohibitions inside a skill: they belong in the system prompt, here they protect nothing

Everything here is measured from the skill text rather than judged by a model, so the numbers are checkable. A parameter weighs more when it is a more common reason for the process to stall.

Quality signals

  • +5Description has no quoted example phrases that should trigger the skill
  • +4Description does not say when NOT to use the skill (false activations)
  • +3Output format is not stated: the model decides each time
  • +1No license
  • +2Single-language instructions
  • +3Description length 192: enough signal without eating the budget
  • +4Structure: 14 headings
  • +3Step-by-step instructions: 16 items
  • +4Has examples (10 code blocks)
  • +3All 7 scripts are documented

Quality base 70; lint remarks subtract, signals add up to 100. Result: 75.