Synthflow alternatives: 9 tools in Voice & Voice Agents
Looking for alternatives to Synthflow? Below are the other Voice & Voice Agents listings we track that bill by card or subscription. Listed A to Z. Pricing lines are from each provider’s own page on the date on the tool page—we do not pick a winner. Synthflow itself: listing · pricing. Category hub: Voice & Voice Agents.
| Tool | Pricing summary | Links |
|---|---|---|
| Bland AI | Start $0.14/min talk time, $0 platform fee; Build $0.12/min + $299/mo platform fee; Enterprise custom. Checked Nov 6, 2026 on bland.ai/pricing. (checked 2026-11-06) | Listing · Pricing |
| Cartesia | Free $0 (20K credits); Pro $5; Startup $49; Scale $299/mo; voice agents $0.03/min; telephony $0.014/min. Checked Nov 6, 2026 on cartesia.ai/pricing. (checked 2026-11-06) | Listing · Pricing |
| Deepgram | Pay as you go Nova-3 monolingual streaming $0.0077/min; Growth prepaid from $4,000/year. Voice Agent Standard $0.075/min. Checked Nov 6, 2026 on deepgram.com/pricing. (checked 2026-11-06) | Listing · Pricing |
| ElevenLabs | Free $0 (10k credits); Starter $6/mo (30k); Creator $22/mo (121k, $11 first month); Pro $99; Scale $299; Business $990. Annual discounts shown on page. Checked Nov 6, 2026 on elevenlabs.io/pricing. (checked 2026-11-06) | Listing · Pricing |
| Murf AI | API: $10 free credit, then pay as you go from $0.01 per 1,000 characters (Falcon 2.1 text-to-speech). Studio plans: see provider. (checked 2026-10-22) | Listing · Pricing |
| Retell AI | Pay as you go from $0.07–$0.31/min for AI voice agents ($10 free credits); chat agents from $0.002+/msg; Enterprise custom. Checked Nov 6, 2026 on retellai.com/pricing. (checked 2026-11-06) | Listing · Pricing |
| Speechify | Free plan (limited voices/speed). Premium $29/month or $139 billed yearly. Checked Nov 6, 2026 on speechify.com/pricing. (checked 2026-11-06) | Listing · Pricing |
| Vapi | $5 free credits; Vapi hosting $0.05/min prepaid; provider costs pass through; Core $29/mo; Pro 10% of hosting fee with $999/mo minimum. Checked Nov 6, 2026 on vapi.ai/pricing. (checked 2026-11-06) | Listing · Pricing |
| WellSaid | Free trial; paid plans: see provider. (checked 2026-10-22) | Listing · Pricing |
Keep exploring
Guides
- What is x402? HTTP 402 payments for APIs and AI agents
- HTTP 402 Payment Required status code explained
- x402 for AI agents: how an agent pays for APIs in USDC
- USDC micropayments: sub-cent payments for APIs and AI agents
- What is MCP? The Model Context Protocol explained
- Agent payments: how AI agents pay for APIs, data and compute
- How to accept USDC for your API (pay-per-call with x402)
- AI agent payment protocols compared: x402, MPP, AP2, ACP and L402
- Pay-per-call AI APIs: no account, no API key, pay in USDC
- How to pay for an API with USDC via x402 (step by step)
- Best x402 APIs for AI agents, by task
- Crypto wallet sanctions screening APIs that accept x402, compared
- Paid MCP servers that accept USDC: x402 pay-per-call MCP tools for AI agents
- Where to list your x402 API: Agentic.Market, x402scan, 402 Index, Agent402, x402dash, x402-trust and PayAPI Market
- Pay-per-call web scraper API for AI agents: URL to Markdown with WebRead (x402)
- x402 agent verification: check an AI agent is registered and verified with AgentGate
- Prompt injection detection API for AI agents: scan text, web pages and MCP tools (InjectScan)
- Domain and email verification API for AI agents: DNS, SPF/DMARC, domain age and disposable checks (DomainCheck)
- OFAC sanctions check API for crypto wallets: screen an address before your agent pays it (PayGuard)
- Check npm dependencies before an AI agent installs them: vulnerable and malicious package API (PkgGuard)
- Website tech stack detection API: a pay-per-call BuiltWith / Wappalyzer alternative for AI agents (StackDetect)
- Base token honeypot checker API for agents that handle tokens (TokenVerdict, x402)
- Is it safe to sign? Pre-sign check API for AI agent wallets (SignCheck)
- Add x402 trust checks to OpenAI Agents SDK and Vercel AI SDK agents
- Prepaid credits for x402 agent APIs: pay once, call with a Bearer key
- x402 vs API keys for AI agents: which should your agent use?
- Check an x402 payTo before your agent pays (CounterpartyCheck)
- Solana token safety check API for agents that handle SPL tokens (SolVerdict, x402)
- Why your x402 endpoint isn't in x402 directories and indexers (and how to fix it)
- Is your site blocking GPTBot and ClaudeBot? Check llms.txt and robots.txt for AI agents (AgentReady)
- Where's funding cheapest to go long BTC right now? How to compare perp funding across venues (PerpRadar)
- Backtest a moving-average cross for your trading agent for 5 cents (TASignal)
- Redact seed phrases and API keys before your AI agent sends them to an LLM (LeakGuard)
- How to read Hyperliquid smart-money positioning from an agent (SmartPerps)
- How an AI agent can find and live-check a paid x402 API for a task (ToolPick)
- Build a read-only crypto trading-research agent with LangGraph or Mastra and x402 MCP tools
- Will Hyperliquid reject this order? A pre-trade order check for trading agents (PerpCheck)
- Audit your agent's tool list before it runs: token cost, schema errors and MCP server checks (ToolFit)
- Give the model 5 tools, not 50: route each agent task to the tools it needs (ToolRoute)
- Currency converter API for AI agents on ECB reference rates (FXRate)
- Crypto price API for AI agents: price snapshots and 24h movers (CryptoPrice)
- Speech-to-text API for AI agents, pay per audio minute (Transcribe)
- x402 facilitators: what they do, how to choose, and a list
- OpenRouter 429 and 402 errors: what they mean and how to fix them
Rankings
- Best x402 APIs
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- x402 market snapshot (data)
- x402 API prices per call (data)
- State of x402: November 2026 (report)
- x402 traffic report (data)
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Best by category
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