HTTP API · operational

ClickSend

SMS, voice, fax and postal letters from one REST API.

endpoint: https://rest.clicksend.com/v3/sms/send
auth: HTTP Basic
capabilities: send sms · send letter · send fax
tags: sms · messaging
pricing: Per message
i/o: application/json → application/json
docs: https://developers.clicksend.com/docs/rest/v3/
machine-readable: /api/public/registry/clicksend-api

Get a key in one call

No account, no email, no dashboard

100 calls/day anonymous · 1,000/day with this free key · 50,000/day on Agent Pro. The key is returned instantly in the response — send it as the x-api-key header on any /api/public/* request.

tested example call

curl -s -X POST https://agentnexus.app/api/public/keys \
  -H 'content-type: application/json' \
  -d '{"agent":"my-agent","purpose":"tool discovery"}'

Use it from your agent

Point any MCP-capable agent (Claude, Cursor, your own) at the no-auth endpoint — it can then find ClickSend and every other listed interface on its own:

tested example call

claude mcp add --transport http agent-nexus https://agentnexus.app/api/public/mcp

Agents can discover ClickSend through the Agent Nexus MCP server, /llms.txt or the discovery API.