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Signal

Signal is a privacy-focused messaging platform that provides end-to-end encrypted communication through open-source applications on mobile and desktop. Their developer ecosystem centers around the open-source Signal Protocol, client SDKs, and server infrastructure, enabling developers to study, audit, and integrate secure messaging capabilities. The Signal Protocol is the most widely deployed end-to-end encryption protocol in the world, used by Signal, WhatsApp, Google Messages, and other platforms.

agent ready

Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.

Kin Score

API Evangelist profiles Signal the way a machine reads it — 31 machine-readable artifacts across 14 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.

Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Signal scores 55.4/100 (developing), with a separate agent-readiness read of 54/100 (agent ready). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.

Kin Score

This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 55.4/100 · developing
Contract Quality 20.8 / 25
Developer Ergonomics 5.2 / 20
Commercial Clarity 10.0 / 20
Operational Transparency 3.4 / 13
Governance 7.3 / 12
Discoverability 8.8 / 10
Agent readiness — 54/100 · agent ready
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 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 7 / 7
Typed Event Surface 6 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3

How we profile Signal

Each block below is one kind of artifact we hold for Signal. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.

APIs 14

Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.

Individual APIs this provider publishes, each with its own machine-readable definition.

Signal Protocol Specifications

The Signal Protocol Specifications define the core cryptographic protocols that underpin Signal's end-to-end encrypted messaging. These include the X3DH (Extended Triple Diffie-...

Signal libsignal SDK

The libsignal SDK provides platform-agnostic APIs used by the official Signal clients and server. It implements the Signal Protocol including the Double Ratchet algorithm, as we...

Signal Android SDK

Signal-Android is the open-source Android client for the Signal encrypted messaging platform. It provides the full messaging experience including end-to-end encrypted text messa...

Signal iOS SDK

Signal-iOS is the open-source iOS client for the Signal encrypted messaging platform. It delivers end-to-end encrypted messaging, voice calls, video calls, and group communicati...

Signal Desktop SDK

Signal-Desktop is the open-source desktop client for the Signal encrypted messaging platform, built with Electron and TypeScript. It provides end-to-end encrypted messaging, voi...

Signal Accounts API

Account management endpoints for configuring account settings, managing capabilities, and account lifecycle operations.

Signal Attachments API

Attachment handling endpoints for uploading and downloading media files associated with messages.

Signal Certificates API

Certificate endpoints for retrieving delivery certificates used in sealed sender message delivery.

Signal Devices API

Device management endpoints for linking, unlinking, and managing devices associated with a Signal account.

Signal Keys API

Pre-key bundle management endpoints for uploading and retrieving public key material used in the Signal Protocol key exchange.

Signal Messages API

Message sending and receiving endpoints for delivering encrypted messages between Signal users.

Signal Profiles API

Profile management endpoints for setting and retrieving user profile information including names, avatars, and capabilities.

Signal Registration API

Account registration endpoints for creating new Signal accounts via phone number verification.

Signal Stickers API

Sticker pack management endpoints for uploading and retrieving sticker packs.

Scroll within the panel for all 14 ·

Open Collections 1

Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Signal Server API

OPEN COLLECTION

Pricing Plans 1

Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.

Published pricing tiers and plan structures.

Signal Plans Pricing

1 plans

PLANS

Rate Limits 1

Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.

Documented rate limits and quota policies.

Signal Rate Limits

1 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.

Cost, billing, and metering signals for API financial operations.

Event Specifications 1

Not every API is request/response. AsyncAPI describes the event-driven and streaming side — the webhooks and channels — so the asynchronous half of the interface is documented the same way the synchronous half is.

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Signal Server Real-Time Events

The Signal Server real-time messaging interface provides WebSocket connections for persistent, bidirectional communication between Signal clients and the server. When a client h...

ASYNCAPI

Semantic Vocabularies 1

JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.

JSON-LD contexts and semantic vocabularies used across these APIs.

Signal Context

0 classes · 10 properties

JSON-LD

Spectral Rules 3

Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.

Signal API Rules

8 rules · 1 errors · 6 warnings

SPECTRAL

Signal API Rules

6 rules · 4 warnings

SPECTRAL

Signal API Rules

8 rules · 2 errors · 4 warnings

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.

Standalone JSON Schema definitions for this provider's data models.

Signal Protocol Entities

0 properties

JSON SCHEMA

JSON Structure 1

JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.

JSON Structure definitions describing this provider's data shapes.

Signal Server Structure

0 properties

JSON STRUCTURE

Examples 2

Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.

Example request and response payloads for these APIs.

Security Posture 3

Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.

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

Signal Authentication

http · 2 schemes

SECURITY

Signal Domain Security

TLSv1.3 · DNSSEC · DMARC

SECURITY

Signal Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.

Recommended x-agentic-access execution contracts for AI agents.

Signal Agentic Access

18 operations · 9 acting

18 operations · 9 acting

AGENTIC

Resources

Every other property we hold for Signal — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.

Documentation 1

Reference material describing how the API behaves

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

Build 1

SDKs, sample code, and the tooling you integrate with

Operate 1

Status, limits, changes, and where to get help

Commercial 2

Pricing, plans, and the legal terms of use

Company 3

The organization behind the API

← All providers · Data indexed from github.com/api-evangelist/signal · machine-readable index on apis.io