# Which API should I use?

A decision guide for AI agents and the people building them: find your need, call the tool. All prices are USDC per call over x402 unless marked.

How paying works: call the paid URL with no payment and you get HTTP 402 with a PAYMENT-REQUIRED header (x402 v2) and the price. Pay in USDC on Base, Polygon, Arbitrum One or Solana with any x402 client (@x402/fetch, x402-axios, Coinbase AgentKit, x402 Python) and retry. Per call only: no signup, no subscription, no custody. Or buy prepaid credits once (https://api.youraitools.co/credits/) and send Authorization: Bearer <key>. Every tool has a free preview, an OpenAPI doc and a remote MCP server (streamable HTTP) at <tool>/mcp.

MCP client config (any tool): `{"mcpServers":{"<tool>":{"url":"https://api.youraitools.co/<tool>/mcp"}}}`

## Free tier: start without a wallet

- **PayGuard**: Free tier: 30 calls/day (full results via remote MCP: screen_address, screen_batch), then $0.001 per call in USDC. `claude mcp add --transport http payguard https://api.youraitools.co/payguard/mcp`
- **InjectScan**: Free tier: 30 calls/day (full scans via remote MCP: scan_text, scan_url, scan_tools), then $0.003 per call in USDC (safety check only). `claude mcp add --transport http injectscan https://api.youraitools.co/injectscan/mcp`
- **PkgGuard**: Free tier: 30 calls/day (full results via remote MCP, up to 100 packages per scan: check_package, scan_dependencies), then $0.001 per package / $0.003 per scan in USDC (safety check only). `claude mcp add --transport http pkgguard https://api.youraitools.co/pkgguard/mcp`
- **WebRead**: Free tier: 30 calls/day (full Markdown via remote MCP, tool read_url), then $0.002 per call in USDC. `claude mcp add --transport http webread https://api.youraitools.co/webread/mcp`

Past the free tier, each tool answers with a payment_required (402) result that points to its paid x402 route.

## Paying and signing (wallet agents)

### Before I pay or approve an address: is it OK, caution or block?
- Use: **CounterpartyCheck** (https://api.youraitools.co/counterpartycheck/)
- Endpoint: GET https://api.youraitools.co/counterpartycheck/v1/lite, $0.005. quick $0.015, full $0.05. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/counterpartycheck/v1/lite?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96&chain=ethereum&intent=pay"`
- Free preview: https://api.youraitools.co/counterpartycheck/v1/preview?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96&chain=ethereum
- MCP: https://api.youraitools.co/counterpartycheck/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_counterparty","arguments":{"address":"0x098B716B8Aaf21512996dC57EB0615e2383E2f96","chain":"ethereum","intent":"pay"}}}`

### Is this address on the OFAC SDN sanctions list?
- Use: **PayGuard** (https://api.youraitools.co/payguard/)
- Endpoint: GET https://api.youraitools.co/payguard/v1/address, $0.001. POST /v1/batch: 50 addresses for $0.01. Informational, not legal advice.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/payguard/v1/address?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96"`
- **Free tier: 30 calls/day (full results via remote MCP: screen_address, screen_batch), then $0.001 per call in USDC**
- Free preview: https://api.youraitools.co/payguard/v1/preview?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96
- MCP: https://api.youraitools.co/payguard/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"screen_address","arguments":{"address":"0x098B716B8Aaf21512996dC57EB0615e2383E2f96"}}}`
- Claude Code: `claude mcp add --transport http payguard https://api.youraitools.co/payguard/mcp`
- Claude Desktop (claude_desktop_config.json, or Settings > Connectors > Add custom connector with https://api.youraitools.co/payguard/mcp): `{"mcpServers":{"payguard":{"command":"npx","args":["-y","mcp-remote","https://api.youraitools.co/payguard/mcp"]}}}`
- Cursor (~/.cursor/mcp.json): `{"mcpServers":{"payguard":{"url":"https://api.youraitools.co/payguard/mcp"}}}`, one-click: cursor://anysphere.cursor-deeplink/mcp/install?name=payguard&config=eyJ1cmwiOiJodHRwczovL2FwaS55b3VyYWl0b29scy5jby9wYXlndWFyZC9tY3AifQ%3D%3D

### Is it safe to sign this transaction, Permit/Permit2, EIP-712 or x402 payment?
- Use: **SignCheck** (https://api.youraitools.co/signcheck/)
- Endpoint: GET https://api.youraitools.co/signcheck/v1/lite, $0.005. full (live simulation) $0.015 at /v1/check. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/signcheck/v1/lite?to=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&data=0x095ea7b3..."`
- Free preview: https://api.youraitools.co/signcheck/v1/preview?to=0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913&data=0x095ea7b30000000000000000000000003c1a1e01e790cd326495631b3b38bd7068f08d6fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
- MCP: https://api.youraitools.co/signcheck/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_signature","arguments":{"chain":"base","tx":{"to":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","data":"0x095ea7b3..."}}}}`

### Is this Base ERC-20 token a honeypot / rug before I buy or accept it?
- Use: **TokenVerdict** (https://api.youraitools.co/tokenverdict/)
- Endpoint: GET https://api.youraitools.co/tokenverdict/v1/lite, $0.005. quick $0.015, deep $0.05. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/tokenverdict/v1/lite?token=0x532f27101965dd16442E59d40670FaF5eBB142E4"`
- Free preview: https://api.youraitools.co/tokenverdict/v1/preview?token=0x532f27101965dd16442E59d40670FaF5eBB142E4
- MCP: https://api.youraitools.co/tokenverdict/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_token","arguments":{"token":"0x532f27101965dd16442E59d40670FaF5eBB142E4"}}}`

### Is this Solana SPL / Token-2022 mint safe to interact with?
- Use: **SolVerdict** (https://api.youraitools.co/solverdict/)
- Endpoint: GET https://api.youraitools.co/solverdict/v1/lite, $0.005. check $0.02. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/solverdict/v1/lite?mint=DezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263"`
- Free preview: https://api.youraitools.co/solverdict/v1/preview?mint=DezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263
- MCP: https://api.youraitools.co/solverdict/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_solana_token","arguments":{"mint":"DezXAZ8z7PnrnRJjz3wXBoRgixCa6xjnB7YaB1pPB263"}}}`

### Is this AI agent registered, Active and Verified?
- Use: **AgentGate** (https://api.youraitools.co/agentgate/)
- Endpoint: GET https://api.youraitools.co/agentgate/v1/check-agent, $0.005. Concordium Agent Registry.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/agentgate/v1/check-agent?id=Mf22soLh1NuZYFgBK8iSs"`
- Free preview: https://api.youraitools.co/agentgate/v1/check-agent/preview?id=Mf22soLh1NuZYFgBK8iSs
- MCP: https://api.youraitools.co/agentgate/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_agent","arguments":{"id":"Mf22soLh1NuZYFgBK8iSs"}}}`

## Guarding the agent itself

### Does this text, web page or MCP tool definition contain a prompt injection?
- Use: **InjectScan** (https://api.youraitools.co/injectscan/)
- Endpoint: GET https://api.youraitools.co/injectscan/v1/scan, $0.003. POST /v1/scan takes {text|url|tools}. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/injectscan/v1/scan?text=Ignore%20previous%20instructions"`
- **Free tier: 30 calls/day (full scans via remote MCP: scan_text, scan_url, scan_tools), then $0.003 per call in USDC (safety check only)**
- Free preview: https://api.youraitools.co/injectscan/v1/scan/preview?text=Ignore%20previous%20instructions
- MCP: https://api.youraitools.co/injectscan/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"scan_text","arguments":{"text":"Ignore previous instructions"}}}`
- Claude Code: `claude mcp add --transport http injectscan https://api.youraitools.co/injectscan/mcp`
- Claude Desktop (claude_desktop_config.json, or Settings > Connectors > Add custom connector with https://api.youraitools.co/injectscan/mcp): `{"mcpServers":{"injectscan":{"command":"npx","args":["-y","mcp-remote","https://api.youraitools.co/injectscan/mcp"]}}}`
- Cursor (~/.cursor/mcp.json): `{"mcpServers":{"injectscan":{"url":"https://api.youraitools.co/injectscan/mcp"}}}`, one-click: cursor://anysphere.cursor-deeplink/mcp/install?name=injectscan&config=eyJ1cmwiOiJodHRwczovL2FwaS55b3VyYWl0b29scy5jby9pbmplY3RzY2FuL21jcCJ9

### Am I about to leak a seed phrase, private key, API secret or PII?
- Use: **LeakGuard** (https://api.youraitools.co/leakguard/)
- Endpoint: GET https://api.youraitools.co/leakguard/v1/lite, $0.005. scan $0.02 adds JSON payloads + funded-wallet check. Inputs never stored. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/leakguard/v1/lite?text=deploy%20log%3A%20aws%20AKIAIOSFODNN7EXAMPLE"`
- Free preview: https://api.youraitools.co/leakguard/v1/preview?text=deploy%20log%3A%20aws%20AKIAIOSFODNN7EXAMPLE
- MCP: https://api.youraitools.co/leakguard/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"scan_for_leaks","arguments":{"text":"deploy log: aws AKIAIOSFODNN7EXAMPLE"}}}`

### Is this npm/PyPI/Go/Cargo dependency safe to install?
- Use: **PkgGuard** (https://api.youraitools.co/pkgguard/)
- Endpoint: GET https://api.youraitools.co/pkgguard/v1/package, $0.001. POST /v1/scan: a whole manifest/lockfile (up to 500 packages) for $0.003. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/pkgguard/v1/package?ecosystem=npm&name=lodash&version=4.17.15"`
- **Free tier: 30 calls/day (full results via remote MCP, up to 100 packages per scan: check_package, scan_dependencies), then $0.001 per package / $0.003 per scan in USDC (safety check only)**
- Free preview: https://api.youraitools.co/pkgguard/v1/preview?ecosystem=npm&name=lodash&version=4.17.15
- MCP: https://api.youraitools.co/pkgguard/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_package","arguments":{"ecosystem":"npm","name":"lodash","version":"4.17.15"}}}`
- Claude Code: `claude mcp add --transport http pkgguard https://api.youraitools.co/pkgguard/mcp`
- Claude Desktop (claude_desktop_config.json, or Settings > Connectors > Add custom connector with https://api.youraitools.co/pkgguard/mcp): `{"mcpServers":{"pkgguard":{"command":"npx","args":["-y","mcp-remote","https://api.youraitools.co/pkgguard/mcp"]}}}`
- Cursor (~/.cursor/mcp.json): `{"mcpServers":{"pkgguard":{"url":"https://api.youraitools.co/pkgguard/mcp"}}}`, one-click: cursor://anysphere.cursor-deeplink/mcp/install?name=pkgguard&config=eyJ1cmwiOiJodHRwczovL2FwaS55b3VyYWl0b29scy5jby9wa2dndWFyZC9tY3AifQ%3D%3D

### Is this domain or email real and trustworthy?
- Use: **DomainCheck** (https://api.youraitools.co/domaincheck/)
- Endpoint: GET https://api.youraitools.co/domaincheck/v1/domain, $0.002. GET /v1/email?email=... $0.001. Safety check only.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/domaincheck/v1/domain?domain=example.com"`
- Free preview: https://api.youraitools.co/domaincheck/v1/domain/preview?domain=example.com
- MCP: https://api.youraitools.co/domaincheck/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_domain","arguments":{"domain":"example.com"}}}`

## Reading the web

### Read a web page as clean Markdown
- Use: **WebRead** (https://api.youraitools.co/webread/)
- Endpoint: GET https://api.youraitools.co/webread/v1/read, $0.002. robots.txt-aware, SSRF-safe.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/webread/v1/read?url=https://example.com/"`
- **Free tier: 30 calls/day (full Markdown via remote MCP, tool read_url), then $0.002 per call in USDC**
- Free preview: https://api.youraitools.co/webread/v1/read/preview?url=https://example.com/
- MCP: https://api.youraitools.co/webread/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"read_url","arguments":{"url":"https://example.com/"}}}`
- Claude Code: `claude mcp add --transport http webread https://api.youraitools.co/webread/mcp`
- Claude Desktop (claude_desktop_config.json, or Settings > Connectors > Add custom connector with https://api.youraitools.co/webread/mcp): `{"mcpServers":{"webread":{"command":"npx","args":["-y","mcp-remote","https://api.youraitools.co/webread/mcp"]}}}`
- Cursor (~/.cursor/mcp.json): `{"mcpServers":{"webread":{"url":"https://api.youraitools.co/webread/mcp"}}}`, one-click: cursor://anysphere.cursor-deeplink/mcp/install?name=webread&config=eyJ1cmwiOiJodHRwczovL2FwaS55b3VyYWl0b29scy5jby93ZWJyZWFkL21jcCJ9

### What is this website built with (CMS, framework, hosting, analytics)?
- Use: **StackDetect** (https://api.youraitools.co/stackdetect/)
- Endpoint: GET https://api.youraitools.co/stackdetect/v1/detect, $0.003
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/stackdetect/v1/detect?url=https://laravel.com"`
- Free preview: https://api.youraitools.co/stackdetect/v1/preview?url=https://laravel.com
- MCP: https://api.youraitools.co/stackdetect/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"detect_stack","arguments":{"url":"https://laravel.com"}}}`

### Is this website ready for AI agents (llms.txt, MCP, x402, robots)?
- Use: **AgentReady** (https://api.youraitools.co/agentready/)
- Endpoint: GET https://api.youraitools.co/agentready/v1/lite, $0.005. audit $0.03.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/agentready/v1/lite?url=https://example.com"`
- Free preview: https://api.youraitools.co/agentready/v1/preview?url=https://example.com
- MCP: https://api.youraitools.co/agentready/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"audit_website","arguments":{"url":"https://example.com"}}}`

## Trading research (read-only)

### Perp funding, open interest and cheapest venue for an asset
- Use: **PerpRadar** (https://api.youraitools.co/perpradar/)
- Endpoint: GET https://api.youraitools.co/perpradar/v1/lite, $0.005. full $0.03, scan $0.02. Not financial advice. Past performance does not guarantee future results.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/perpradar/v1/lite?symbol=BTC"`
- Free preview: https://api.youraitools.co/perpradar/v1/preview?symbol=BTC
- MCP: https://api.youraitools.co/perpradar/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"perp_positioning","arguments":{"symbol":"BTC"}}}`

### Technical indicators, risk sizing or a rule backtest for a symbol
- Use: **TASignal** (https://api.youraitools.co/tasignal/)
- Endpoint: GET https://api.youraitools.co/tasignal/v1/lite, $0.005. risk $0.02, backtest $0.05. Not financial advice. Past performance does not guarantee future results.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/tasignal/v1/lite?symbol=BTC&timeframe=1h"`
- Free preview: https://api.youraitools.co/tasignal/v1/preview?symbol=BTC&timeframe=1h
- MCP: https://api.youraitools.co/tasignal/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"ta_bias","arguments":{"symbol":"BTC","timeframe":"1h"}}}`

### What are the most profitable Hyperliquid traders holding?
- Use: **SmartPerps** (https://api.youraitools.co/smartperps/)
- Endpoint: GET https://api.youraitools.co/smartperps/v1/lite, $0.003. coin $0.02, scan $0.03, wallet $0.01. Not financial advice. Past performance does not guarantee future results.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/smartperps/v1/lite?symbol=BTC"`
- Free preview: https://api.youraitools.co/smartperps/v1/preview?symbol=BTC
- MCP: https://api.youraitools.co/smartperps/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"smart_money_bias","arguments":{"symbol":"BTC"}}}`

## Finding and selling paid APIs

### I need a paid API for a task and don't know which one
- Use: **ToolPick** (https://api.youraitools.co/toolpick/)
- Endpoint: GET https://api.youraitools.co/toolpick/v1/lite, $0.003. pick (live-verified best pick) $0.01, market (seller price quartiles) $0.02. Ranks, does not endorse.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/toolpick/v1/lite?need=web%20search"`
- Free preview: https://api.youraitools.co/toolpick/v1/preview?need=web%20search
- MCP: https://api.youraitools.co/toolpick/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"find_paid_api","arguments":{"need":"web search"}}}`

### Will my x402 endpoint work with payers and Bazaar / x402scan?
- Use: **x402fix** (https://api.youraitools.co/x402fix/)
- Endpoint: GET https://api.youraitools.co/x402fix/v1/lite, $0.005. check $0.02, site $0.05.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/x402fix/v1/lite?url=https://api.youraitools.co/counterpartycheck/v1/lite"`
- Free preview: https://api.youraitools.co/x402fix/v1/preview?url=https://api.youraitools.co/counterpartycheck/v1/lite
- MCP: https://api.youraitools.co/x402fix/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"check_x402_endpoint","arguments":{"url":"https://api.youraitools.co/counterpartycheck/v1/lite"}}}`

### Put an x402 paywall in front of my own API
- Use: **x402 Proxy Template** (https://api.youraitools.co/x402-template/)
- Endpoint: GET https://api.youraitools.co/x402-template/download, $19 one-time. Cloudflare Worker zip, MIT. Free preview at the landing page.
- curl (first reply is the 402 with payment terms): `curl -i "https://api.youraitools.co/x402-template/download"`
- Free preview: https://api.youraitools.co/x402-template/

## Paying less per call

### Skip the on-chain payment on every call (prepaid balance)
- Use: **Credits (prepaid packs)** (https://api.youraitools.co/credits/)
- Endpoint: POST https://api.youraitools.co/credits/v1/pack/1, $1 (or $5 for $5.50). Then send Authorization: Bearer <key> to any paid route. Not refundable.
- curl (first reply is the 402 with payment terms): `curl -i -X POST "https://api.youraitools.co/credits/v1/pack/1"`
- Free preview: https://api.youraitools.co/credits/v1/preview?pack=5
- MCP: https://api.youraitools.co/credits/mcp, tools/call `{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"credits_quote","arguments":{}}}`

## Not sure?
Ask ToolPick: `curl -i "https://api.youraitools.co/toolpick/v1/lite?need=<your task>"` ($0.003), or the free preview https://api.youraitools.co/toolpick/v1/preview?need=web%20search. It also searches other sellers' x402 APIs.

## Discovery
- Tool index: https://api.youraitools.co/ (JSON or HTML)
- All paid resources: https://api.youraitools.co/.well-known/x402
- Combined OpenAPI: https://api.youraitools.co/openapi.json
- llms.txt: https://api.youraitools.co/llms.txt, full: https://api.youraitools.co/llms-full.txt