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StableLinq

iMessage, RCS & SMS for the Open Agentic Web
stablelinq.dev

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Agents are becoming a real customer segment — they discover services, compare prices, pay per call, and act without a human in the loop. StableLinq brings that model to conversational messaging: any agent on AgentCash can send and manage iMessage, RCS, and SMS through Linq, paying with USDC micropayments instead of signing up for another API account.

No API keys. No billing dashboards. No subscriptions. Tell your agent who to text.

Agentic commerce for messaging

Most messaging APIs were built for apps with human operators — sign up, generate keys, negotiate rate limits, wire up Stripe. Agents don't work that way. They need to discover what's available, see the price upfront, pay, and move on.

StableLinq is listed on the Open Agentic Web like any other AgentCash service. An agent discovers the endpoint, gets a quote, pays via x402 or MPP, and the message goes out on iMessage (with RCS and SMS fallback). Reads — chat history, send ledger, warmth checks — are free with wallet identity.

Agent                         StableLinq
  |                                |
  |-- "text this number" -------->|
  |<-- 402 + price ----------------|
  |-- pays USDC, retries --------->|
  |<-- delivered ------------------|

That's it. One wallet balance, one discovery flow, native messaging protocols.

What agents can do

• Send messages — iMessage first, then RCS, then SMS. Reactions, voice memos, media, attachments.
• Follow up in existing threads — warm conversations cost less than cold outreach.
• Check before sending — iMessage/RCS capability checks, warmth pre-checks, thread history.
• Respect reply limits — block after 10 consecutive unanswered messages to the same recipient (line-wide).
• Manage their own sends — edit, delete, or react to messages they paid for.

Every agent shares one outbound line. Your wallet owns what you paid to send; the thread belongs to the conversation.

Pricing

Pay per call, quoted before you commit. Call POST /api/messages/warmth (free) for the exact send cost — read quoted_price_usd before telling the user. Do not cite maxPrice ($26.25 on POST /api/messages) as the send cost; that is the wallet authorization ceiling for worst-case batch sends.

New recipient (cold)	$0.50 — text-only opener, 50/day cap
Follow-up (warm)	$0.05–$1.25 surge pricing
Unanswered limit	10 consecutive outbound without a reply — then blocked until they respond. If blocked but they replied and the webhook was missed, the next send reconciles from the Linq thread.
Everything else	$0.02 flat
Reads	Free with wallet auth

Cold openers must be plain text — no links or media on a first touch. Call POST /api/messages/warmth (free) before stating cold/warm or quoting cost — returns quoted_price_usd plus line-wide warmth, not per wallet.

For agents

Install AgentCash, fund your wallet, and discover StableLinq:

npx @agentcash/discovery stablelinq.dev

Full endpoint schemas, composition patterns, and pricing rules: stablelinq.dev/llms.txt

• Warmth + price: call POST /api/messages/warmth before telling the user cold/warm or send cost (required — returns quoted_price_usd and line-wide warmth, not per wallet).
• Schema probe: check_endpoint_schema confirms request shape only — not send cost. Do not cite discovery maxPrice as the quote.

OpenAPI: stablelinq.dev/openapi.json

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Linq powers delivery · AgentCash powers payments