AI agent tools: the APIs agents use to act
26 services in 6 categories that let an AI agent post, email, take payments, use a phone, drive a browser and search the web.
Prices, MCP servers and licences checked 2026-10-17 on each vendor's own pages, with a source link on every field. “not verified” means we could not confirm it.
Short answer: Most of these tools now publish an official MCP server, so the practical differences are price shape (per post, email, minute, browser hour or request), whether a free tier exists, and whether you can self-host. Start with the category below that matches the action your agent needs to take.
Social posting
APIs and MCP servers that let an agent schedule and publish posts to X, LinkedIn, Instagram, TikTok and other networks.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| Ayrshare | Products that post on behalf of many end customers, where billing per customer profile fits better than per channel or seat. | No free plan: 28-day free trial with Launch plan access [source, checked 2026-10-17] | Premium $149/month: 1 profile; Launch $299: up to 10 profiles; Business $599: 30 profiles, then $8.99 per profile to 100 and $3.49 to 500 [source, checked 2026-10-17] |
| Buffer | Individuals and small teams who want a free start and an agent that drafts into a queue they review. | Free: 3 channels, 10 scheduled posts per channel, 1 API key [source, checked 2026-10-17] | Essentials $5 per channel/month, Team $10 per channel/month, billed yearly (annual billing saves 20%) [source, checked 2026-10-17] |
| Postiz | Agents that schedule posts across many networks for one brand or a few, with the option to self-host the open-source version. | No free plan: 7-day free trial on every plan (self-hosting the open-source code is free) [source, checked 2026-10-17] | Standard $29/month: 5 channels; Team $39 (10), Pro $49 (30), $99 plan (100 channels). Yearly: $23, $31, $39, $79 per month [source, checked 2026-10-17] |
| Zernio (formerly Late) | Developers who want usage-based pricing per connected account with every feature on, and a free start for two accounts. | First 2 connected accounts free, no card (X accounts need a card) [source, checked 2026-10-17] | $6 per account/month for accounts 3–10, $3 for 11–100, $1 above 100; DMs: first 10,000 sent a month free, then metered [source, checked 2026-10-17] |
Transactional email APIs an agent can send through, and agent inboxes that also receive and reply.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| AgentMail | Agents that need their own inbox to receive, read and reply to email, not just send. | Free: 3 inboxes, 3,000 emails/month (100/day), 3 GB [source, checked 2026-10-17] | Developer $20/month: 10 inboxes, 10,000 emails, 10 custom domains; Startup $200/month: 150 inboxes; add-ons $2 per inbox, domain or 1,000 emails [source, checked 2026-10-17] |
| Mailgun | Senders who want a permanent free tier for testing and published volume rates down to $0.40 per 1,000. | Free: 100 emails/day, 1 custom sending domain [source, checked 2026-10-17] | Basic from $15/month: 10,000 emails ($1.80 per extra 1,000); Foundation $35/month: 50,000; Scale $90/month: 100,000 [source, checked 2026-10-17] |
| Postmark | Transactional email where you want separate message streams, published overage rates and longer log retention. | Developer: 100 emails/month, no overages, does not expire [source, checked 2026-10-17] | Basic $15/month: 10,000 emails, then $1.80 per 1,000; Pro $16.50 ($1.30 per 1,000); Platform $18 ($1.20 per 1,000) [source, checked 2026-10-17] |
| Resend | Developers sending transactional email from code who want a usable free tier, React Email and an official MCP server. | Free: 3,000 emails/month, 100/day, 3 domains [source, checked 2026-10-17] | Pro $20/month: 50,000 emails, then $0.90 per 1,000; Scale $90/month: 100,000 emails [source, checked 2026-10-17] |
| Twilio SendGrid | High-volume senders who also want Twilio's other channels on the same account. | 60-day free trial: 100 emails/day, no credit card [source, checked 2026-10-17] | Essentials from $19.95/month; Pro from $89.95/month (dedicated IPs); Premier custom [source, checked 2026-10-17] |
Payments
Payment processors and merchants of record an agent can use to create checkouts, subscriptions and invoices.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| Lemon Squeezy | Existing users selling digital products who want a merchant of record; new projects should read the 2026 update first. | No monthly fee [source, checked 2026-10-17] | 5% + 50¢ per transaction; the pricing page lists extra fees in some cases (e.g. transactions outside the US) [source, checked 2026-10-17] |
| Paddle | SaaS and app businesses that want a merchant of record with one flat checkout fee and an official MCP server. | No monthly fees [source, checked 2026-10-17] | 5% + 50¢ per checkout transaction; custom pricing for high volume [source, checked 2026-10-17] |
| Polar | Developers selling software or subscriptions who want an open-source merchant of record with fees that drop on higher plans. | Starter: no monthly fee, 5% + 50¢ per transaction [source, checked 2026-10-17] | Pro $20/month: 3.8% + 40¢; Growth $100: 3.6% + 35¢; Scale $400: 3.4% + 30¢ [source, checked 2026-10-17] |
| Stripe | Products that want full control of checkout, billing and payouts, and agent tooling from the payment provider itself. | No setup or monthly fees [source, checked 2026-10-17] | 2.9% + 30¢ per successful domestic card transaction (US) [source, checked 2026-10-17] |
Phone, SMS and voice
Carrier APIs for numbers and texts, and voice-agent platforms that let an AI answer and place calls.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| Retell AI | Teams that want an all-in per-minute price for voice agents and SOC 2 and HIPAA without a separate add-on fee. | $10 free credits; 20 concurrent calls included [source, checked 2026-10-17] | Pay as you go: $0.07–$0.31 per minute for voice agents; chat agents from $0.002 per message [source, checked 2026-10-17] |
| Telnyx | Cost-sensitive SMS and voice at volume, where you want the platform rate and carrier pass-through shown separately. | No platform fee; pay as you go [source, checked 2026-10-17] | SMS $0.004 per message part + carrier fee; Voice API $0.002/min + SIP trunk fee; numbers from $1.00/month [source, checked 2026-10-17] |
| Twilio | Teams that want the widest set of channels (SMS, voice, WhatsApp, email) on one account with pay-as-you-go rates. | Free trial, no credit card [source, checked 2026-10-17] | US SMS $0.0083 per segment sent or received; local number $1.15/month; local calls $0.0140/min out, $0.0085/min in [source, checked 2026-10-17] |
| Vapi | Developers building voice agents who want to choose their own speech, model and voice providers. | $5 free credits, 1 Vapi phone number, 4 concurrent calls [source, checked 2026-10-17] | Pay as you go from $0.05/min plus providers; Core package $29/month: 5 numbers, 10 concurrent calls [source, checked 2026-10-17] |
Browser automation
Hosted browsers, open-source agent libraries and MCP servers that let an agent open pages, click, type and read.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| Browser Use | Developers who want an open-source agent library and, optionally, cheap pay-as-you-go cloud browsers. | One-time $1 credit for eligible signups; the open-source library is free [source, checked 2026-10-17] | Pay as you go, top-ups from $5: browsers $0.02/hour, residential proxy $5/GB, agents at model cost + 20% [source, checked 2026-10-17] |
| Browserbase | Production agents that need many hosted browsers at once, with automatic captcha solving. | Free: 3 concurrent browsers, 1 browser hour [source, checked 2026-10-17] | Developer $20/month: 100 browser hours then $0.12/hour, 25 concurrent; Startup $99/month: 500 hours then $0.10/hour, 100 concurrent [source, checked 2026-10-17] |
| Hyperbrowser | Agents that mix browser sessions with page fetch, search and extraction under one credit balance. | Free: 5,000 credits, 1 concurrent session [source, checked 2026-10-17] | Startup $30/month: $30 usage, 25 concurrent sessions; Scale $100/month: $100 usage, 100 concurrent sessions [source, checked 2026-10-17] |
| Playwright MCP | Coding agents and local workflows where a browser on your own machine is enough and you pay nothing. | Free, open source [source, checked 2026-10-17] | No paid plan [source, checked 2026-10-17] |
| Steel | Teams that want an open-source browser API they can self-host, with a hosted cloud for production. | Launch $0: $30 one-time credits, 10 concurrent sessions, sessions up to 15 minutes, $0.10/browser hour [source, checked 2026-10-17] | Scale $250/month: $100 credits monthly, 100 concurrent sessions, $0.08/browser hour, sessions up to 1 hour [source, checked 2026-10-17] |
Web search and scraping
Search engines and scrapers that return LLM-ready results, so an agent can find and read current web pages.
| Tool | Best for | Free tier | Entry paid price |
|---|---|---|---|
| Brave Search API | Agents that need results from an independent web index, prepaid with no subscription. | $5 in free credits every month per API plan (up to $20 a month across plans, per the page) [source, checked 2026-10-17] | Search $5 per 1,000 requests [source, checked 2026-10-17] |
| Exa | Agents that need fast web search with full page contents, priced per request. | $10 credits every month plus a $10 onboarding bonus, no payment method [source, checked 2026-10-17] | Search from $4 per 1,000 requests; contents $1 per 1,000 pages; deep search $12–15 per 1,000 [source, checked 2026-10-17] |
| Firecrawl | Turning web pages and whole sites into clean markdown or structured data for an agent, with an open-source core. | Free: 1,000 credits/month (about 500 searches or 1,000 pages), no card [source, checked 2026-10-17] | Hobby $19/month billed monthly ($16 billed annually): 5,000 credits [source, checked 2026-10-17] |
| Tavily | Agents that want search, extract and crawl behind one credit balance with a simple free tier. | Researcher: 1,000 API credits/month, no card [source, checked 2026-10-17] | Pay as you go $0.008 per credit; Project $30/month: 4,000 credits [source, checked 2026-10-17] |
Head-to-head comparisons
- Postiz vs Ayrshare
- Resend vs Postmark
- Twilio vs Telnyx
- Vapi vs Retell AI
- Browserbase vs Steel
- Paddle vs Lemon Squeezy
- Exa vs Tavily
Alternatives: Twilio alternatives · Twilio SendGrid alternatives · Browserbase alternatives · Lemon Squeezy alternatives
FAQ
What are AI agent tools?
Services an AI agent calls to do something outside the chat: publish a post, send or receive email, take a payment, text or call a phone, operate a browser or search the web. Most expose a REST API, and many now publish an MCP server so clients such as Claude, ChatGPT or Cursor can call them directly.
What is an MCP server?
A Model Context Protocol server describes a service's actions as tools that an AI client can discover and call. For example, Stripe's remote MCP server lets an agent call the Stripe API, and Playwright MCP lets it drive a browser.
How did you choose these tools?
We started with 6 categories of actions agents commonly take, then listed tools whose pricing and features we could check on the vendor's own pages on 2026-10-17. Tools whose pricing we could not read are left out until we can verify them.
Are these affiliate links?
Some tool pages have an affiliate “Visit” button, marked as an affiliate link with a disclosure on that page; see our disclosure page. Comparison tables, order and descriptions are the same whether or not a vendor has an affiliate programme, and source links always go to the vendor's own pages.
Is this a ranking?
No. Tools are listed alphabetically within each category with the same fields, and we publish no star ratings. Sponsored placements, if any, are labelled and never change order or facts.
Data and method
Every field restates the vendor's pricing page, docs or official repository on the checked date, with the link. Download the dataset: agent-tools.json · agent-tools.csv (CC BY 4.0). Corrections with a source link: submit form. Also on Evals Review: LLM evaluation tools for testing the agents themselves.