An SMS marketing API is the technical connection that lets your business software send and receive text messages automatically without manual work.
An SMS marketing API is the technical connection that lets your business software send and receive text messages automatically without manual work. When your scheduling system needs to send appointment reminders, when your e-commerce platform needs to notify customers about orders, when your CRM needs to trigger follow-up messages based on customer behavior, the API handles those communications.
Most business owners evaluating SMS APIs aren't developers. You're trying to figure out which provider will actually work reliably, integrate smoothly with your existing systems, and not create headaches six months from now when something breaks. The technical specifications matter less than whether the API does what you need without constant troubleshooting.
This guide covers what actually matters when choosing an SMS API provider. Not every technical specification (most don't impact your business), but the features and considerations that determine whether an API integration succeeds or becomes an expensive mistake.
Strip away the technical jargon and an SMS API does three things: sends text messages when your software tells it to, receives replies from customers and passes them to your software, and confirms whether messages were delivered successfully.
The complexity comes from doing these three things reliably at scale. Sending one text message is easy. Sending 10,000 messages in an hour, ensuring 98%+ get delivered, handling replies correctly, managing opt-outs automatically, and keeping everything compliant with regulations requires sophisticated infrastructure.
When you evaluate SMS API providers, you're really evaluating infrastructure quality and reliability. Can they deliver your messages quickly and consistently? Do they have redundancy so your messages still send if one carrier has problems? Can their system handle your peak volume without slowing down or failing?
Think of it like choosing a shipping company. FedEx and a local courier both deliver packages, but FedEx has infrastructure (sorting facilities, tracking systems, backup routes) that makes them reliable at scale. SMS APIs work the same way. The underlying task (send message) is simple, but doing it reliably for thousands of customers requires serious infrastructure.
Sakari built its API specifically for business reliability. The platform handles message routing across carriers automatically, maintains redundant connections to ensure delivery even during carrier issues, and processes hundreds of messages per second without performance degradation. For businesses where SMS communication is critical (appointment reminders, order confirmations, security alerts), this infrastructure reliability matters more than any individual feature.
Every SMS API provider claims high delivery rates. The question is what they mean by "delivery" and whether their numbers hold up in real-world use.
True delivery rate means the percentage of messages that successfully reach recipients' phones out of total valid messages sent. Valid is the key word. If you send to disconnected numbers or landlines that can't receive SMS, those shouldn't count against delivery rate. But some providers include those failures in their metrics to make their delivery rates look worse than they are, or exclude them to make rates look better.
Legitimate SMS API providers achieve 97-99% delivery rates for valid mobile numbers in good standing. Anything below 95% indicates infrastructure problems or carrier relationship issues. Anything claiming 99.9%+ is probably manipulating how they calculate the metric.
What actually causes delivery failures for that remaining 1-3%? Temporary carrier issues, phone turned off or out of service area when message sends, message filtered as spam by carrier, number recently ported to different carrier and routing hasn't updated, or customer's inbox full (yes, this still happens).
Good API providers handle these gracefully. They retry temporary failures automatically, provide detailed delivery status for every message so you know what happened, and maintain relationships with carriers to minimize filtering and routing issues.
Ask potential providers: What's your actual delivery rate for US mobile numbers? Can you show delivery rate data from last 90 days? What happens when message fails to deliver, do you retry automatically? How quickly will I know if message didn't deliver?
Sakari maintains 98%+ delivery rates and provides detailed delivery receipts (DLRs) for every message showing exact delivery status. When messages fail, the platform retries automatically for temporary failures and provides clear failure reasons for permanent failures (disconnected number, invalid format, etc.). This transparency lets you clean your contact lists and improve future delivery rates.
Message delivery speed matters for time-sensitive communications. Appointment reminder that sends 3 hours late isn't useful. Security alert that arrives 10 minutes after the event doesn't help.
SMS APIs measure speed in two ways: latency (time from API call to message queuing) and throughput (how many messages can be sent per second).
Latency should be under 1 second for properly configured APIs. You make API call, message queues for delivery within 1 second. Then actual delivery to recipient's phone takes another 1-5 seconds depending on carrier processing. Total time from API call to message on customer's phone: 2-6 seconds typically.
If provider's latency regularly exceeds 5 seconds, their infrastructure is overloaded or poorly designed. Your time-sensitive messages will miss their windows.
Throughput matters when sending campaigns or processing high volumes. Can the API handle 1,000 appointment reminders going out simultaneously at 9am when your scheduling system triggers them? Or does it choke, queue messages for 20 minutes, and send reminders sporadically over the next half hour?
Different businesses need different throughput. Small practice sending 50 messages daily needs maybe 10 messages per second capacity. Large operation sending 10,000 messages for campaign needs 100-500 messages per second.
Ask providers: What's your message throughput per second? What happens if I need to send large batch quickly? Do you throttle or rate limit, and how does that work?
Sakari handles several hundred messages per second without throttling for typical business accounts. For businesses needing higher throughput, dedicated infrastructure can process thousands of messages per second. The platform automatically handles peak loads (like Monday morning appointment reminders) without performance degradation.
Your SMS API connects to your business systems and customer data. Security matters because breaches could expose customer phone numbers, message content, or let bad actors send spam through your account.
Most SMS APIs use API key authentication. You get unique key when setting up account, include that key in every API call, and the system verifies it's you making the request. Simple and works fine if you protect the API key properly.
More sophisticated implementations use OAuth or token-based authentication where keys expire and must be refreshed. This is more secure but adds complexity. For most business use cases, API key authentication is sufficient if implemented correctly.
What matters more than authentication method is how you handle API keys in your systems. Never hardcode API keys in client-side code where users can see them. Never commit API keys to public repositories. Store them as environment variables or in secure configuration management. Rotate keys periodically (every 6-12 months minimum).
Good API providers also offer IP whitelisting. You tell them which IP addresses should be allowed to use your API key, and they reject requests from anywhere else. If your API key somehow leaks, it's useless to attackers unless they're making requests from your whitelisted IPs.
Ask providers: What authentication methods do you support? Can I rotate API keys without downtime? Do you offer IP whitelisting or other security features? How are messages encrypted in transit and at rest?
Sakari uses secure API key authentication with support for IP whitelisting, provides easy key rotation through dashboard, and encrypts all messages in transit using TLS. Message content is also encrypted at rest in Sakari's systems. For businesses with compliance requirements (healthcare, finance), Sakari meets security standards required by those industries.
Rate limits control how many API requests you can make in given timeframe. Providers implement rate limits to prevent abuse and ensure fair resource allocation across customers.
Common rate limit structure: X messages per second, Y API calls per minute, Z total messages per day. For example: 100 messages per second, 1,000 API calls per minute, 50,000 messages per day.
Rate limits rarely affect normal business operations. You're probably not hitting these thresholds unless you're sending massive campaigns or making API calls inefficiently.
Where rate limits cause problems: Poorly designed integration that makes separate API call for every message instead of batching. Sudden spike in volume (Black Friday for retail, season start for home services) that exceeds normal limits. Testing and development that hammers API with rapid requests.
Good practice: Batch messages when possible. If sending 500 appointment reminders, don't make 500 separate API calls. Make one API call with array of 500 messages. This is faster, more efficient, and stays well within rate limits.
Ask providers: What are your rate limits? Can limits be increased if my business grows? What happens when I hit rate limit, do requests fail or queue? Will you alert me if I'm approaching limits?
Sakari's rate limits are generous for typical business use (hundreds of messages per second, thousands of API calls per minute). For businesses needing higher limits, Sakari works with you to adjust based on legitimate business needs. The system provides clear error messages when limits are approached and queues requests rather than dropping them when possible.
Webhooks let the SMS API push information to your systems instead of you constantly polling for updates. When customer replies to your text, when message delivery status changes, when customer opts out, the API sends that information to your system immediately via webhook.
This is critical for two-way conversations and real-time notifications. Without webhooks, your system would need to constantly ask "any new replies?" "any delivery updates?" every few seconds. Inefficient and still not truly real-time.
With webhooks, your system receives instant notification when something happens. Customer texts STOP, webhook fires immediately, your system processes opt-out, customer is suppressed from future messages within seconds. This is how you comply with regulations requiring immediate opt-out processing.
Good webhook implementations include: retry logic (if your system is temporarily down, API retries webhook delivery), signature verification (proves webhook actually came from API provider, not attacker), detailed payload (includes all relevant information about the event), and clear documentation showing exactly what webhooks fire for which events.
Ask providers: What webhook events do you support? How do webhooks get retried if my system is temporarily unavailable? How do I verify webhook authenticity? Can I test webhooks before going live?
Sakari provides comprehensive webhooks for all critical events (incoming messages, delivery receipts, opt-outs, sending errors). Webhooks include cryptographic signatures for verification, implement exponential backoff retry logic, and can be tested using Sakari's webhook testing tools before integration goes live. For implementation details, review HubSpot SMS integration showing webhook usage in practice.
Developer documentation determines how quickly your team can integrate the API and how much frustration they experience along the way. Poor documentation turns 2-week integration into 2-month nightmare.
Good API documentation includes: clear getting started guide that works (too many docs have broken examples), complete endpoint reference with every parameter explained, working code examples in multiple languages, explanation of error codes and how to handle them, webhook documentation with payload examples, and rate limit and authentication details.
The test of good documentation: Can competent developer who's never used your API successfully send first message within 30 minutes of reading docs? If answer is no, documentation is inadequate.
Beyond written documentation, good providers offer: interactive API explorer (test API calls directly from browser), Postman collection or similar tools, integration guides for common platforms, and active developer community or forum.
Ask providers: Can I see your API documentation before committing? Do you have code examples in [language your team uses]? How current is the documentation? When was it last updated?
Sakari provides comprehensive API documentation with working examples in Python, PHP, Node.js, C#, and other common languages. The documentation includes interactive API explorer for testing, Postman collection for development, and regular updates reflecting platform changes. For businesses without internal developers, Sakari offers integration assistance and pre-built integrations with common platforms. Review SMS marketing automation strategies showing API usage in real business contexts.
SMS API pricing typically follows per-message model. You pay small amount (usually $0.01-0.04) per message sent. Some providers also charge monthly platform fee.
What makes pricing complicated: Different rates for different countries. Different rates for different message types (marketing vs transactional). Volume discounts that kick in at certain thresholds. Carrier fees that vary by recipient's network. Charges for phone number rental if you need dedicated number.
Watch for hidden costs: Inbound message fees (some providers charge for receiving replies), lookup fees (some charge to verify number before sending), MMS fees (picture messages cost more than text), toll-free number fees (vs standard local numbers), support fees (some providers charge for technical support), and overage fees (penalty pricing if you exceed plan limits).
Transparent pricing shows: Per-message cost clearly stated. Any platform fees or minimum monthly charges. Inbound message pricing if applicable. Number rental fees if using dedicated numbers. Volume discount structure if offered.
Ask providers: What's the all-in cost to send 1,000 messages in my region? Are there any fees beyond per-message cost? Do you charge for inbound messages? What's the cost if I need dedicated phone number? Do you offer volume discounts?
Sakari uses transparent per-message pricing with no hidden fees. You pay for messages sent (outbound) and messages received (inbound). Phone number rental is separate clear fee. Volume discounts are available for higher usage. No platform fees, no minimum monthly charges, no support fees. You only pay for what you use. For detailed cost analysis, explore SMS marketing ROI framework.
APIs break. Carriers have issues. Edge cases emerge. Your integration hits unexpected scenario. When this happens, provider support quality determines whether problem gets resolved in 2 hours or 2 weeks.
Support evaluation criteria: Response time for technical issues (hours, not days). Availability of technical support staff who actually understand the API (not just customer service). Access to account manager or technical contact for complex issues. Quality of troubleshooting tools (logs, delivery reports, debugging features). Proactive notification when provider has issues affecting your service.
Some providers offer tiered support. Basic plan gets email support with 24-48 hour response. Premium plan gets phone support and faster response. Enterprise gets dedicated technical account manager. Evaluate based on how critical SMS is to your business operations.
Ask providers: What support channels do you offer? What's typical response time for technical issues? Do you provide technical account managers? How do you notify customers about service issues? Can I see message logs and delivery details for troubleshooting?
Sakari provides email and phone support with technical staff who understand API integrations deeply. Response times for technical issues are typically under 4 hours during business hours, faster for critical issues affecting message delivery. Dashboard provides comprehensive message logs, delivery reports, and debugging tools. For businesses with complex integrations, Sakari offers dedicated technical support and account management.
Before deciding you need custom API integration, check whether provider offers pre-built integration for your platform. Most businesses use common software (Salesforce, HubSpot, Shopify, scheduling platforms) where pre-built integrations exist.
Pre-built integrations are maintained by API provider, receive updates automatically, have been tested extensively, include support and documentation, and cost nothing extra beyond API usage. Custom API integration requires developer time, ongoing maintenance, your team handles bugs, and you're responsible for keeping integration current.
Use custom API when: Your software is proprietary or custom-built. Your workflow requires logic not possible with pre-built integrations. You need to combine multiple systems in ways pre-built integrations don't support. You're building product that includes SMS as feature.
Use pre-built integration when: Your platform has supported integration. Pre-built integration does 90%+ of what you need. You want something working this week, not 3 months from now. You'd rather not maintain custom code.
Sakari offers pre-built integrations with major platforms including HubSpot, Salesforce, scheduling software, and e-commerce platforms. For businesses needing custom integration, Sakari's API is well-documented with developer support available. Most businesses start with pre-built integrations and only move to custom API if specific needs aren't met.
See how different businesses use SMS APIs to solve actual operational problems.
Medical and dental practices: Integrate with practice management software (Dentrix, Eaglesoft, etc.). API automatically sends appointment reminders based on appointment schedule. Receives confirmation replies from patients. Updates appointment status in practice management system based on patient responses. Reduces no-shows by 40-50% without manual work from front desk staff.
Home services (HVAC, plumbing, electrical): Integrate with scheduling and dispatch software. Sends customer text when technician is assigned to job. Sends "on my way" text 30 minutes before arrival. Sends post-service text requesting review with direct link. Customers know exactly when technician arriving, less "where are you?" calls to office.
E-commerce: Integrate with Shopify, WooCommerce, or custom shopping cart. Order placed, API sends confirmation text. Order ships, API sends tracking number. Delivery approaching, API sends notification. Customer responds with questions, webhook routes to support team. Reduces "where is my order?" support tickets by 60%.
Real estate: Integrate with CRM. New lead comes in from website, API sends immediate text response. Lead books showing, API sends confirmation and reminder. After showing, API sends follow-up asking for feedback. Faster lead response improves conversion rates. For comprehensive automation examples, explore intelligent SMS routing strategies.
Choose SMS API provider based on what actually matters for your business, not technical specifications you'll never use.
Priority 1: Reliability and delivery rates. If messages don't consistently reach customers, nothing else matters.
Priority 2: Integration compatibility. Does it work with your existing systems easily, or will integration be constant headache?
Priority 3: Support quality. When things break (they will), can you get help quickly from people who know the product?
Priority 4: Pricing transparency. Hidden fees and confusing pricing structures cause budget problems later.
Priority 5: Documentation quality. If you're doing custom integration, good documentation saves weeks of developer time.
Everything else is secondary. Fancy features you'll never use don't deliver business value.
Sakari built its SMS API specifically for business reliability and ease of integration. The platform handles technical complexity automatically, provides clear documentation and support, uses transparent pricing, and integrates with major business platforms out of the box. For businesses where SMS communication is operational necessity (not nice-to-have), Sakari delivers the reliability and support required.
Ready to integrate SMS messaging into your business systems with reliable API built for service businesses? Start your free trial with Sakari and access comprehensive API documentation, pre-built integrations, and technical support to get your integration live quickly.
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