CallSign website screenshot

CallSign

Callsign is a digital trust platform for fraud prevention, authentication, and identity intelligence. Its Intelligence Engine combines behavioral biometrics, device fingerprinting, telco intelligence, and threat ensembling with an orchestration layer that applies dynamic interventions across customer journeys - login and access, online payments, account creation, and Zero Trust network access - to recognize and authenticate users passively. The Authentication Suite (Callsign One) delivers passwordless, low-friction authentication, and the platform targets account takeover, social engineering and scams, malware and bots, SIM swap, call divert, and synthetic identity. Callsign integrates via REST APIs and web and mobile SDKs, and is certified to ISO/IEC 27001 with SOC 2 attestation. Added to the API Evangelist network from the Accel portfolio and enriched from Callsign's public developer surface.

CallSign is profiled on the APIs.io network. Tagged areas include Company, Ai, Identity, Authentication, and Fraud Prevention.

CallSign’s developer surface includes documentation, API reference, authentication, support, engineering blog, and 12 more developer resources.

🌐 Visit website 📡 Source on GitHub
23.7/100 emerging ▬ flat Agent 16/100 agent aware Full breakdown ↓
scored 2026-07-27 · rubric v0.5
0 APIs
CompanyAiIdentityAuthenticationFraud PreventionBehavioral BiometricsSecurityFintech

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 23.7/100 · emerging
Contract Quality 0.0 / 25
Developer Ergonomics 8.3 / 20
Commercial Clarity 7.4 / 20
Operational Transparency 1.4 / 13
Governance 0.0 / 12
Discoverability 6.8 / 10
Agent readiness — 16/100 · agent aware
Machine-Readable Contract 0 / 18
Agentic Access Contract 0 / 15
MCP Server 0 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 4 / 4
Consent & Bot Identity 3 / 3
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/callsign: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

Security Posture 3

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Callsign Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Callsign Vulnerability Disclosure

security.txt · contact published

SECURITY

Callsign Trust Center

ISO/IEC 27001, SOC 2

SECURITY

Resources

Get Started 1

Portal, sign-up, and the first successful call

DeveloperPortal
DeveloperPortal

Documentation 2

Reference material describing how the API behaves

Documentation
Documentation
 APIReference
APIReference

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

WellKnown
WellKnown
 LLMsTxt
LLMsTxt

Access & Security 7

Authentication, authorization, and security posture

Authentication
Authentication
 Compliance
Compliance
 TrustCenter
TrustCenter
 Security
Security
 VulnerabilityDisclosure
VulnerabilityDisclosure
 DomainSecurity
DomainSecurity
 SecurityTxt
SecurityTxt

Scroll for all 7

Operate 1

Status, limits, changes, and where to get help

Support
Support

Commercial 2

Pricing, plans, and the legal terms of use

TermsOfService
TermsOfService
 PrivacyPolicy
PrivacyPolicy

Company 2

The organization behind the API

Website
Website
 Blog
Blog

Source (apis.yml)

apis.yml Raw ↑ 
aid: callsign
name: CallSign
description: Callsign is a digital trust platform for fraud prevention, authentication, and identity intelligence. Its Intelligence
  Engine combines behavioral biometrics, device fingerprinting, telco intelligence, and threat ensembling with an orchestration
  layer that applies dynamic interventions across customer journeys - login and access, online payments, account creation,
  and Zero Trust network access - to recognize and authenticate users passively. The Authentication Suite (Callsign One) delivers
  passwordless, low-friction authentication, and the platform targets account takeover, social engineering and scams, malware
  and bots, SIM swap, call divert, and synthetic identity. Callsign integrates via REST APIs and web and mobile SDKs, and
  is certified to ISO/IEC 27001 with SOC 2 attestation. Added to the API Evangelist network from the Accel portfolio and enriched
  from Callsign's public developer surface.
url: https://raw.githubusercontent.com/api-evangelist/callsign/refs/heads/main/apis.yml
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
image: https://www.callsign.com/media/general-images/in-page-images/_1200x630_crop_center-center_none/Homepage-Account-login-access-person-with-phone-content-1640x1200.jpg
x-type: company
x-source: vc-portfolio
x-backed-by:
- accel
x-tier: stub
x-tier-reason: portfolio-lead
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-18'
tags:
- Company
- Ai
- Identity
- Authentication
- Fraud Prevention
- Behavioral Biometrics
- Security
- Fintech
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Website
  url: http://www.callsign.com
- type: DeveloperPortal
  url: https://www.callsign.com/developers
- type: Documentation
  url: https://docs.callsign.com/
- type: APIReference
  url: https://docs.callsign.com/
- type: Authentication
  url: https://docs.callsign.com/auth
- type: Support
  url: https://support.callsign.com
- type: Blog
  url: https://www.callsign.com/news
- type: TermsOfService
  url: https://www.callsign.com/terms-of-use
- type: PrivacyPolicy
  url: https://www.callsign.com/privacy-notice
- type: Compliance
  url: https://www.callsign.com/security-and-compliance
- type: TrustCenter
  url: security/callsign-trust-center.yml
- type: Security
  url: security/callsign-vulnerability-disclosure.yml
- type: VulnerabilityDisclosure
  url: security/callsign-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/callsign-domain-security.yml
- type: SecurityTxt
  url: well-known/callsign-security.txt
- type: WellKnown
  url: well-known/callsign-well-known.yml
- type: LLMsTxt
  url: llms/callsign-llms.txt
x-enrichment:
  date: '2026-07-19'
  status: backfilled
  pass: local-v1
  note: backfilled from .gitignore signal + verified work evidence