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, Artificial Intelligence, Identity, Authentication, and Fraud Prevention.

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

🌐 Visit website 📡 Profile data on GitHub

23.8/100 emerging ▬ flat Agent 3/100 human only Front door AI 2/6 trace Heartbeat 93/100 alive saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

0 APIs

Company Artificial Intelligence Identity Authentication Fraud Prevention Behavioral Biometrics Security Fintech

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 23.8/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 6.9 / 17

Access Clarity 6.3 / 17

Operational Transparency 1.2 / 11

Contract Governance 0.0 / 10

Discoverability 4.7 / 9

Regulatory Posture 4.1 / 15

Agent readiness — 3/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

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 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the AI & Biometrics regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0

12 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points
Access Clarity scores 36.8 — up to +12.6 composite points
Contract Governance scores 0.0 — up to +12.0 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/callsign/apis.yml: open an issue on github.com/api-evangelist/callsign to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
Biometrics Testing (biometric recognition vendors, identity verification depth)	distribution	19.2 (thin)	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

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

Compliance

TrustCenter

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)

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
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - security
  generated: '2026-11-06'
  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: '0.23'
created: '2026-07-17'
modified: '2026-07-18'
x-docs-platform: stoplight
x-docs-platform-confidence: high
x-docs-platform-checked: 2026-09-21
tags:
- Company
- Artificial Intelligence
- Identity
- Authentication
- Fraud Prevention
- Behavioral Biometrics
- Security
- Fintech
tags_raw:
- 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

CallSign API — frequently asked questions

How do I authenticate with the CallSign API?

CallSign uses bearer-token authentication.

Is the CallSign API ready for AI agents?

CallSign has a Kin Score of 23.8 out of 100 (emerging) and an Agent Readiness score of 2.5 (human-only), scored by API Evangelist on 2026-11-06.

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