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Callsign

Routes messages between AI agents from different labs through handles, consent-gated requests and a hash-chained action ledger.

Actively maintained

SupportAgentsOpen source
callsign.im ↗
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Callsign: data, price, alternatives
At a glancechecked Oct 24, 2026

not read yet

Use

For
owners of AI agents from different labs who want those agents to message each other
Activity
Actively maintainedrelease 9 days ago
Company
Majily LLCprivacy policy
How it runs
API
App Store
26 ratingsiPhone & iPad · updated Sep 29, 2022
Used for
  • send requests so one AI agent can message another
  • keep a ledger of what each agent did
  • approve or freeze agent messages from one place
Worth knowingcomputed from what we read · each with its source
Your datawhat they publish, each line with its page · read Oct 29, 2026

“We never sell personal data, never use Content to train AI models and never show ads.”

privacy policy ↗

These are Callsign's own statements, read from its pages. We did not audit them. A line that is missing was not found on the pages we read; it does not mean the practice is absent.

How a program reaches itfound, not claimed · read Oct 29, 2026
  • MCP serverim.callsign/callsignverified in the MCP registry
  • Stateanswers, requires sign-inchecked 2026-10-29
  • Address to connectapi.callsign.im/mcp

MCP server details →

This card as JSON, for your agent →

Each line is something a program found when it went looking: the registry entry, the server's own answer, a spec that parses. A missing line means we did not find it, not that it does not exist.

Alternatives in Supportby use, among tools still maintained

Figure and bar: visits/mo, estimate · year: online since

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Questions this page answers
  • What is Callsign?

    Routes messages between AI agents from different labs through handles, consent-gated requests and a hash-chained action ledger. It is listed in the Atlas under Support and made by Majily LLC.

  • Who is Callsign for?

    owners of AI agents from different labs who want those agents to message each other

  • Is Callsign still maintained?

    Actively maintained: release 9 days ago.

  • Who owns Callsign?

    Callsign is run by Majily LLC, per its privacy policy (2026-10-29).

  • Does Callsign train AI on your data?

    No, per its privacy policy (2026-10-29): “We never sell personal data, never use Content to train AI models and never show ads.”

  • Is Callsign safe?

    We do not audit vendors. What Callsign publishes, read 2026-10-29: on training with your data, “We never sell personal data, never use Content to train AI models and never show ads.”.

  • Does Callsign have an iPhone app?

    Yes: “Callsign” on the App Store, rated 2 from 6 ratings; current version released 2022-09-29.

  • What are alternatives to Callsign?

    In Support, by use: S.C.A.L.A. AI OS, AgentChat, AgentDM, AgentMesh, Tandem.

How we read a tool

No votes, no reviews, no vendor claims. Every week a crawler reads each tool's own site and a few public registries, and the words on the card are bands over what it read.

  • Use: visits to the site (estimated), installs from npm and PyPI, presence in Chrome's usage report.
  • Activity: the newest release on GitHub, npm or PyPI; the newest dated page on the site; open roles on a public jobs board.
  • Price: the vendor's own pricing page, read with the date. A figure is printed only when it is on that page.
  • The line and the use cases are written by us from the homepage, one tool at a time, and refused when they repeat the vendor's marketing.

How AI assistants read each site — the reading vendors ask us about — is on each tool's own visibility page.

How we read every tool → · By INITE Atlas Desk