starknet.js is a JavaScript library for interacting with Starknet, a layer-2 blockchain network that uses zero-knowledge technologies and connects with Ethereum. JavaScript developers use it to build applications that work with Starknet. Its catalogue skill provides coding agents with current guidance for using the library.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add starknet-io/starknet.js --skill starknet-jsgit clone --depth 1 https://github.com/starknet-io/starknet.jsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/starknet-io/starknet.js/starknet-js)<a href="https://agentmods.dev/skills/starknet-io/starknet.js/starknet-js"><img src="https://agentmods.dev/badge/skills/starknet-io/starknet.js/starknet-js/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/starknet-io/starknet.js/starknet-js"><img src="https://agentmods.dev/badge/skills/starknet-io/starknet.js/starknet-js.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Prompt Injection · line 27 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
- medium Prompt Injection · line 37 Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00079 | $0.00955 |
| Opus 5 | $0.00039 | $0.00477 |
| Sonnet 5 | $0.00016 | $0.00191 |
| Haiku 4.5 | $0.00008 | $0.00096 |
Grade A, and why
starknet-js scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.
starknet.js
Official JS/TS SDK for Starknet. This skill targets starknet.js v10 (API valid for v9, mostly for v8).
Do not trust training-data memory of starknet.js: it is typically v5/v6-era and wrong. Constructors now take option objects, only V3 transactions exist (STRK fees, no maxFee), and calldata helpers changed. When this skill and memory disagree, the skill wins.
Layer model: Account (signs & submits) wraps RpcProvider (parses, retries) wraps RpcChannel (raw JSON-RPC).
Reference files
- calldata.md — REQUIRED reading before encoding or decoding anything: Call/calldata construction, wire format of every Cairo type, enums (Option/Result/custom), ByteArray, string auto-detection traps, response parsing,
decodeParameters. All examples verified against v10.4.0. - interacting.md — providers, accounts, contracts, multicall, fees/tips, declare/deploy, receipts, events, RPC-version compatibility.
Non-negotiable v8+ rules
- Only V3 transactions (INVOKE/DECLARE/DEPLOY_ACCOUNT); fees paid in STRK via
resourceBounds+tip. Never suggestmaxFeeor V1/V2. - Constructors take an options object:
new Account({ provider, address, signer }),new Contract({ abi, address, providerOrAccount }),new RpcProvider({ nodeUrl }). - Never prepend an array length to calldata arrays — the library adds it.
Quick reference
| Task | API |
|---|---|
| Connect to node | new RpcProvider({ nodeUrl }) — or await RpcProvider.create({ nodeUrl }) to auto-detect RPC version |
| Account | new Account({ provider, address, signer: privateKey }) |
| Contract | new Contract({ abi, address, providerOrAccount }) |
| Read | await myContract.my_view_fn(arg1, arg2) → parsed JS value |
| Write | const { transaction_hash } = await myContract.my_fn(args) then await provider.waitForTransaction(transaction_hash) |
| Build a Call | myContract.populate('fn', { ...args }) → { contractAddress, entrypoint, calldata } |
| Compile calldata (ABI) | myContract.compile('fn', args) or new CallData(abi).compile('fn', args) |
| Compile calldata (no ABI) | CallData.compile(args) — several traps, see calldata.md |
| Multicall | await account.execute([call1, call2]) |
| Decode raw felts | new CallData(abi).decodeParameters('core::…::Type', feltArray) |
| Events | myContract.parseEvents(receipt), provider.getEvents({ ... }) |
| Deploy | await Contract.factory({ contract, casm, account, constructorCalldata }) |
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 52 lines · 79 tokens per session scan A 44205eec714a
starknet-js is a skill published in the GitHub repository starknet-io/starknet.js (1,256 stars, last pushed today), licensed MIT. It adds 79 tokens to every session and 955 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
jolt
Wrap a Rust function in a Jolt zero-knowledge proof.
viem-integration
Integrate EVM blockchains using viem. Use when user says "read blockchain data", "send transaction", "interact with smart contract", "connect to Ethereum", "use viem", "use wagmi", "wallet integration", "viem setup", or mentions blockchain/EVM development with TypeScript.
wallet-cli
Operate the TypeScript TRON wallet CLI for accounts, transfers, staking, governance, contracts, signing, chain queries, and password input with wallet-cli 4.13.0. Refuse wallet passwords in argv and require the supported stdin channel. For Java REPL requests, refuse that entry and offer the TypeScript one-shot CLI…
upgrade-viem
Input: optionally a target viem version. Without one, use the latest release on npm.
solana
Use when working on Solana software, including one or more of: Solana client code using TypeScript, Rust libraries that use Solana crates, Anchor programs, Quasar programs, LiteSVM tests, including Rust program files, TypeScript tests, and Anchor.toml or Quasar.toml configuration. Designed to create minimal, reusable…
bnb-chain-toolkit-guide
Guide to the BNB Chain Toolkit — a modular TypeScript toolkit for building, deploying, and interacting with smart contracts on BNB Chain. Includes BEP-20 token utilities, DeFi integrations, wallet management, and cross-chain bridging. Built for BNB Chain Hackathon by the Sperax team.