AWS Communication Developer Services: Which Channel Should the Agent Use (2026)

On 31 March 2026 AWS announced RCS for Business in End User Messaging. On 25 September 2026 the same group published AI agent skills for the AWS MCP Server, covering End User Messaging and Amazon SES. Those two dates are the reason to reopen the channel decision. The model did not get a new inbox. The pipes did.

This is part 1 of AWS Communication Developer Services. The channel guides are RCS, SMS, WhatsApp, and the SES skill bridge.

Communication Developer Services is AWS’s name for the send path: End User Messaging (RCS and SMS), End User Messaging Social (WhatsApp), and Amazon SES. The September 2026 partner hackathon uses that list. Push is on the End User Messaging pricing page and is outside that list.

FactualMinds has no published CDS engagement. Every dollar below is list price from the End User Messaging pricing page, read 29 September 2026.

Two agents, and they are not the same

The September skills talk to a coding agent in Claude Code, Codex, Cursor, or Kiro. You ask it to verify an SES identity, or to build a branded RCS agent and send yourself a card. That agent is a setup assistant. It uses the AWS MCP Server and a skill file. It does not sit in your customer’s messages.

The customer-facing agent is the other one. A person texts your brand. Inbound lands on Amazon SNS (or EventBridge, or Firehose). A Lambda function calls the model. The reply goes back out on the same channel. That pattern is the public multi-channel sample for SMS and WhatsApp, and it is the pattern the RCS docs describe when they say inbound messages go to SNS.

We recommend you finish the coding-agent setup before you connect the customer-facing agent. The trade-off is a week of registration with nothing in production. Connecting Bedrock to a testing RCS agent feels like a launch. A testing agent only delivers to phones you enrolled. Customers on the real network get nothing, and you will not see that in a demo to your own handset.

The customer-facing agent may look up an order. It may not refund, change an address, or change a price. Those stay a proposal a named person approves. That rule is the same one in how AI agents reduce support work and human-in-the-loop approvals.

Four channels, four jobs

WhatsApp wins the where-is-my-order row when has_whatsapp_thread is yes. The customer already opened the window. Starting a new RCS thread beside an open WhatsApp thread splits the history.

The bill you can calculate before anyone replies

US Rich RCS, outbound, per delivered 160-byte segment: $0.00700 AWS + $0.00494 carrier = $0.01194. Charged on delivery, not on the attempt.

US Rich Media (a card, a carousel, a file, a webview, a map pin, or a calendar chip): $0.02000 + $0.00949 = $0.02949 per delivered message.

Suggested replies, a dial chip, and an Open URL that uses the full browser stay on the Rich meter. A photo upgrades the message.

List-price arithmetic, not a client bill — 10,000 delivered one-segment US Rich texts cost $119.40. The same 10,000 as Rich Media cost $294.90. The card costs $175.50 more per 10,000 deliveries, before the $200 monthly agent maintenance fee that the pricing page lists for every country. US setup adds $500 once and $200 a year for brand vetting.

WhatsApp’s AWS fee is $0.005 per outbound message, and $0.002 for India Authentication and Utility. Inbound is $0.001. Meta’s fee sits on top. AWS says it converts Meta’s INR card using the 1 July 2026 exchange rate and may refresh that USD figure on the first day of each quarter. Do not budget WhatsApp from the AWS fee alone.

US MMS is a published pair: $0.02 base + $0.01 carrier. US outbound voice is $0.013 per minute and needs a voice-enabled long code. US SMS transport is a per-carrier CSV on the same pricing page. This series does not invent a single US SMS cent.

What broke — A team treats “RCS is one message on the phone” as “RCS is one segment on the bill.” The rich-message post is right that an RCS text arrives as one bubble. The US rate card still meters Rich text per 160 bytes. A 400-character status update is three segments if it stays text, or one Rich Media charge if you wrap it in a card. Run both numbers in the worksheet before you pick the layout.

What we recommend

For a customer-facing text agent in the US, send plain updates through a phone pool: the RCS agent plus one dedicated SMS originator registered for the same use case. Pool sending on SendTextMessage tries RCS first and, if there is no RCS signal within 25 seconds, sends SMS as a separate attempt. That 25-second figure is in the AI prompt on the Sending RCS messages page. It is asynchronous. It is not a second channel inside the same request.

The trade-off: the SMS fallback comes from a phone number, so the customer loses the logo on that attempt. Direct send with the RCS agent ARN has no fallback at all. Account-level send, where you omit the originator, can fall back onto a number registered for a different use case. AWS calls that a compliance risk. One pool per use case.

Rich cards use SendRcsMessage and an explicit FallbackConfiguration. Chips do not survive into SMS. Write the SMS body as its own sentence. The fallback originator has to be a phone number or sender ID, not the pool and not the RCS agent.

Email is the receipt. The SES skill on 25 September 2026 helps a coding agent verify an identity and send a first production message. It does not make email a two-way support thread. Read the SES bridge and then the existing pricing and warm-up posts.

Registration is the schedule

The API call is the short part.

• US SMS on a 10-digit long code needs a company, a campaign, and a number. The pricing page lists $4.50 company registration, $12.50 for the public-profit verification email, $41.50 company vetting, $10 a month for a regular campaign ($2 low-volume), and $1 a month per number. Toll-free is $2 a month and is a different registration, not a shortcut around 10DLC if you still want a 10DLC. The 10DLC vetting form lists a $40 non-refundable vetting fee. Confirm which line you are about to pay.
• RCS testing can be a same-day demo to your own phone. Country launch is a separate registration per country. The launch guide says AWS supports launches in 22 countries, and that carrier approval should be planned in several months. You can send to a carrier as soon as that carrier is active. The others fall back to SMS only if you are on a pool or account-level send.
• WhatsApp needs a WhatsApp Business account and templates for anything you start.
• SES needs a verified identity. Volume on a new dedicated IP is a warm-up problem, not a skill problem.

Reproduce this — Open the channel planner CSV and the README. Leave the milestone rows alone. Fill one plan row per job. If you cannot name the registration blocker, you are not ready to connect the model.

What to do this week

1. Fill the four plan rows. OTP, where-is-my-order, promo, receipt.
2. If the receipt row is not ses, change it. Then read the pricing plans post before you lease an IP.
3. For where-is-my-order, decide RCS-plus-SMS or WhatsApp. Do not stand up both until one of them can receive a reply.
4. Keep refunds, address changes, and price changes on the approval queue in human-in-the-loop.
5. Only then install the 25 September 2026 skill for the channel you actually chose.

What this post doesn’t cover

Push notifications, Amazon Connect chat, and Pinpoint journeys. MMS and voice are short sections in the SMS guide, not their own strategy. Per-carrier US SMS cents live in AWS’s CSV. Meta’s country rate card is Meta’s. This series does not publish a delivery percentage, because we have not run that send.

FAQ

What is AWS Communication Developer Services?

AWS uses the name for the channels a partner or builder sends on. End User Messaging covers RCS and SMS. End User Messaging Social covers WhatsApp. Amazon SES covers email. Push notifications are a real End User Messaging channel, and the September 2026 CDS hackathon rules say push does not count as CDS usage.

Which channel should a support agent use first?

If the customer already has an open WhatsApp thread, answer there. If they do not, and a verified brand name on the phone matters, use a phone pool that tries RCS and falls back to a dedicated SMS number registered for the same use case. Use SES for the receipt and the long answer. Do not start with a rich card.

When should I not use RCS?

Skip RCS when you only need a one-time passcode and you do not already have an approved OTP agent, when the destination country is not in the launch list, or when you cannot wait through carrier review. The country-launch guide says approval can take several months. A testing agent cannot message production numbers.

When should I not put the agent on WhatsApp?

Skip WhatsApp when the customer has never written to you there. Business-initiated messages outside the customer care window need an approved template. You also pay Meta’s fee on top of the AWS fee, and that Meta fee is not a single global number.

What goes wrong if the coding agent and the customer agent get mixed up?

The 25 September 2026 skills tell a coding assistant how to verify an SES identity or build an RCS agent in your account. They do not answer a customer’s where-is-my-order text. Wiring inbound SNS events to a model without a human approval step is how a refund gets sent because a prompt said so.

Does FactualMinds have a published CDS engagement?

No. The prices in this series are AWS list prices read on 29 September 2026. There is no delivery-rate lift and no tickets-down percentage in these posts.