Cosign

Cosign is the command-line client of the Sigstore project for signing, verifying, and storing container images, OCI artifacts, blobs, and in-toto attestations. Cosign supports keyless signing using OpenID Connect identity providers (Google, GitHub, Microsoft) by obtaining short-lived certificates from the Fulcio certificate authority and recording signing events in the Rekor transparency log. Signatures and attestations are stored alongside the signed artifact in any OCI-compliant registry, and cosign integrates with policy controllers, KMS providers, hardware tokens, and SBOM workflows for software supply chain security.

Cosign is listed with 3 APIs on the APIs.io network, including Sigstore Rekor API (consumed), Sigstore Fulcio API (consumed), and 1 more. Tagged areas include Apache 2.0, Attestation, CLI, Code Signing, and Containers.

Cosign’s developer surface includes documentation, getting-started guide, release notes, engineering blog, CLI, changelog, sandbox, and 32 more developer resources.

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41.1/100 developing ▬ flat Agent 22/100 agent aware open core · Apache-2.0 Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessOpen

3 APIs 3 Agent Skills

Apache 2.0 Attestation CLI Code Signing ContainersFulcioGoKeylessOCI OpenID Connect Open SourceRekorSigstore Supply Chain Transparency Log Verification

Kin Score

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

Composite quality — 41.1/100 · developing

Contract Quality 4.5 / 19

Developer Ergonomics 11.7 / 15

Access Clarity 0.0 / 15

Operational Transparency 4.9 / 10

Contract Governance 1.6 / 9

Discoverability 5.2 / 8

Regulatory Posture 3.4 / 15

Open Source Surface 6.5 / 10

Agent readiness — 22/100 · agent aware

Machine-Readable Contract 18 / 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 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 7 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 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 Horizontal (data, software, accessibility, platform) 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.

Open Source Surface applies to this provider. This product is open source and we read its repository directly, so Open Source Surface carries 10 points of the composite. It is scored from what the repository actually publishes — a security policy, a contribution guide, a release history, a code of conduct — read live from the provider rather than inferred from our own catalog pointers. This facet adds; nothing was taken away to make room for it. An open-source project is not excused from the commercial facets, because exemption would strip it of the points it does earn. If we have the wrong repository, or this product is not open source, say so on your provider repo and we will drop the facet rather than have you publish against 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 75 points between them, because both conditional facets apply and carry 25 points together. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 75% 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):

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)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document

8 more unmet checks in the Agent Readiness table above.

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

Access Clarity scores 0.0 — up to +20.0 composite points
Contract Quality scores 24.0 — up to +19.0 composite points
Contract Governance scores 18.2 — up to +9.8 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/cosign/apis.yml: open an issue on github.com/api-evangelist/cosign 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 →

Standards implemented 3

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenID Connect

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

Sigstore

tagged — the provider's own APIs.json carries the standard as a tag; implementation not verified

OpenAPI

measured — observed by APIs.io (published)

APIs 3

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

Cosign CLI

Cosign is a command-line tool for signing, verifying, and storing container images and OCI artifacts. It supports keyless signing, hardware-backed keys, KMS providers, in-toto a...

Sigstore Rekor API (consumed)

Rekor is the Sigstore transparency log that cosign writes to and reads from when recording and verifying signing events. The public Rekor service exposes a REST API at rekor.sig...

Sigstore Fulcio API (consumed)

Fulcio is the Sigstore certificate authority that issues short-lived X.509 code-signing certificates bound to OIDC identities. Cosign calls the Fulcio public CA at fulcio.sigsto...

Agent Skills 3

Packaged agent skills for driving this provider's APIs from an AI assistant.

Attest an SBOM and verify it

AGENT SKILL

Sign a container image keylessly

AGENT SKILL

Verify a container image signature

AGENT SKILL

Cosign API pricing

Pricing Plans 1

Published pricing tiers and plan structures.

Cosign Plans Pricing

0 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Cosign Rate Limits

0 limits

RATE LIMITS

FinOps 1

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

Cosign Finops

FINOPS

Security Posture 3

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

Cosign Authentication

6 schemes

SECURITY

Cosign Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Cosign Vulnerability Disclosure

Hackerone

SECURITY

Resources

Get Started 3

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

DeveloperPortal

DeveloperPortal

Sandbox

Sandbox

Documentation 2

Reference material describing how the API behaves

ContributionGuide

ContributionGuide

Documentation

Documentation

Agent Surfaces 3

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

AgentSkill

AgentSkill

X-MCPServerCandidate

X-MCPServerCandidate

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Lifecycle

Conformance

Conventions

ErrorCatalog

DataModel

Build 6

SDKs, sample code, and the tooling you integrate with

CodeOfConduct

CodeOfConduct

GitHubOrganization

GitHubRepository

Packages

SDKs

CLI

Access & Security 4

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Security

Security

VulnerabilityDisclosure

VulnerabilityDisclosure

Authentication

Authentication

Operate 9

Status, limits, changes, and where to get help

IssueTracker

ReleaseNotes

Community

Slack

RoadMap

ChangeLog

StatusPage

Deprecation

RateLimits

Scroll for all 9

Commercial 3

Pricing, plans, and the legal terms of use

FinOps

FinOps

License

License

Plans

Plans

Company 3

The organization behind the API

LinkedIn

Website

Website

Blog

Blog

Other 1

Properties that don't map to a standard resource type

Installation

Installation

Source (apis.yml)

aid: cosign
name: Cosign
kind: opensource
description: Cosign is the command-line client of the Sigstore project for signing, verifying, and storing container images,
  OCI artifacts, blobs, and in-toto attestations. Cosign supports keyless signing using OpenID Connect identity providers
  (Google, GitHub, Microsoft) by obtaining short-lived certificates from the Fulcio certificate authority and recording signing
  events in the Rekor transparency log. Signatures and attestations are stored alongside the signed artifact in any OCI-compliant
  registry, and cosign integrates with policy controllers, KMS providers, hardware tokens, and SBOM workflows for software
  supply chain security.
url: https://raw.githubusercontent.com/api-evangelist/cosign/refs/heads/main/apis.yml
deliveryModel:
  model: open-core
  license: Apache-2.0
  license_evidence:
    repo: sigstore/cosign
    spdx: Apache-2.0
    stars: 6326
  open_source: true
  commercial: true
  callable_host: false
  label: Open core · an OSS project plus a commercial hosted product
  confidence: medium
  source:
  - pricing
  - repository-license
  generated: '2026-09-25'
  method: derived
accessModel:
  pricing: unknown
  onboarding: open
  trial: false
  try_now: false
  public: true
  gated: none
  gated_source:
  - onboarding
  label: Open access
  confidence: medium
  source:
  - authentication
  - rate-limits
  - security
  - sandbox
  generated: '2026-11-06'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/cosign.png
type: Index
access: Public
position: Producing
tags:
- Apache 2.0
- Attestation
- CLI
- Code Signing
- Containers
- Fulcio
- Go
- Keyless
- OCI
- OpenID Connect
- Open Source
- Rekor
- Sigstore
- Supply Chain
- Transparency Log
- Verification
tags_raw:
- Apache 2.0
- Attestations
- CLI
- Code Signing
- Containers
- Fulcio
- Go
- Keyless
- OCI
- OIDC
- Open Source
- Rekor
- Sigstore
- Supply Chain
- Transparency Log
- Verification
- Open-Source
created: '2026-03-26'
modified: '2026-09-07'
specificationVersion: '0.23'
apis:
- aid: cosign:cosign-cli
  name: Cosign CLI
  description: Cosign is a command-line tool for signing, verifying, and storing container images and OCI artifacts. It supports
    keyless signing, hardware-backed keys, KMS providers, in-toto and SLSA attestations, and transparency log inclusion. The
    CLI is the primary user interface and does not expose its own HTTP API.
  humanURL: https://docs.sigstore.dev/cosign/
  properties:
  - type: Documentation
    url: https://docs.sigstore.dev/cosign/
  - type: GettingStarted
    url: https://docs.sigstore.dev/quickstart/quickstart-cosign/
  - type: Installation
    url: https://docs.sigstore.dev/cosign/system_config/installation/
  - type: GitHubRepository
    url: https://github.com/sigstore/cosign
  - type: Reference
    url: https://github.com/sigstore/cosign/tree/main/doc
  tags:
  - CLI
  - Containers
  - Keyless
  - OCI
  - Signing
- aid: cosign:rekor-api
  name: Sigstore Rekor API (consumed)
  description: 'Rekor is the Sigstore transparency log that cosign writes to and reads from when recording and verifying signing
    events. The public Rekor service exposes a REST API at rekor.sigstore.dev with operations for creating log entries, retrieving
    entries by index or UUID, fetching log info and proofs, and searching the index. Ownership: Rekor is a sibling project
    of Cosign inside the same GitHub organization (github.com/sigstore) and the same OpenSSF Sigstore project. It is recorded
    here as a CONSUMED dependency of the Cosign CLI, not as an API Cosign produces; the Rekor contract is profiled in its
    own right under all/sigstore.'
  humanURL: https://docs.sigstore.dev/logging/overview/
  baseURL: https://rekor.sigstore.dev
  properties:
  - type: Documentation
    url: https://docs.sigstore.dev/logging/overview/
  - type: OpenAPI
    url: https://raw.githubusercontent.com/sigstore/rekor/main/openapi.yaml
  - type: GitHubRepository
    url: https://github.com/sigstore/rekor
  tags:
  - Rekor
  - REST
  - Sigstore
  - Transparency Log
- aid: cosign:fulcio-api
  name: Sigstore Fulcio API (consumed)
  description: 'Fulcio is the Sigstore certificate authority that issues short-lived X.509 code-signing certificates bound
    to OIDC identities. Cosign calls the Fulcio public CA at fulcio.sigstore.dev during keyless signing to obtain a certificate
    for a verified identity. Ownership: Fulcio is a sibling project of Cosign inside the same GitHub organization (github.com/sigstore)
    and the same OpenSSF Sigstore project; its published contract at fulcio.swagger.json declares host fulcio.sigstore.dev,
    matching the baseURL below. It is recorded here as a CONSUMED dependency of the Cosign CLI, not as an API Cosign produces.'
  humanURL: https://docs.sigstore.dev/certificate_authority/overview/
  baseURL: https://fulcio.sigstore.dev
  properties:
  - type: Documentation
    url: https://docs.sigstore.dev/certificate_authority/overview/
  - type: OpenAPI
    url: https://raw.githubusercontent.com/sigstore/fulcio/main/fulcio.swagger.json
  - type: GitHubRepository
    url: https://github.com/sigstore/fulcio
  tags:
  - CA
  - Certificates
  - Fulcio
  - OpenID Connect
  - Sigstore
  tags_raw:
  - CA
  - Certificates
  - Fulcio
  - OIDC
  - Sigstore
common:
- type: FinOps
  url: finops/cosign-finops.yml
- type: IssueTracker
  url: https://github.com/sigstore/cosign/issues
- type: CodeOfConduct
  url: https://github.com/sigstore/cosign/blob/main/CODE_OF_CONDUCT.md
- type: ContributionGuide
  url: https://github.com/sigstore/cosign/blob/main/CONTRIBUTING.md
- type: DomainSecurity
  url: security/cosign-domain-security.yml
- type: LinkedIn
  url: https://www.linkedin.com/company/sigstore
- type: Website
  url: https://www.sigstore.dev/
- type: Documentation
  url: https://docs.sigstore.dev/cosign/
- type: GettingStarted
  url: https://docs.sigstore.dev/quickstart/quickstart-cosign/
- type: Installation
  url: https://docs.sigstore.dev/cosign/system_config/installation/
- type: GitHubOrganization
  url: https://github.com/sigstore
- type: GitHubRepository
  url: https://github.com/sigstore/cosign
- type: ReleaseNotes
  url: https://github.com/sigstore/cosign/releases
- type: Blog
  url: https://blog.sigstore.dev/
- type: Community
  url: https://www.sigstore.dev/community
- type: Slack
  url: https://sigstore.slack.com/
- type: License
  url: https://github.com/sigstore/cosign/blob/main/LICENSE
- type: Security
  url: https://github.com/sigstore/cosign/security
- type: RoadMap
  url: https://github.com/sigstore/community/blob/main/ROADMAP.md
- type: DeveloperPortal
  url: https://docs.sigstore.dev/
- type: Packages
  url: packages/cosign-packages.yml
- type: SDKs
  url: packages/cosign-packages.yml
- type: CLI
  url: cli/cosign-cli.yml
- type: ChangeLog
  url: changelog/cosign-changelog.yml
- type: Lifecycle
  url: lifecycle/cosign-lifecycle.yml
- type: StatusPage
  url: https://status.sigstore.dev/
- type: Deprecation
  url: https://github.com/sigstore/cosign/blob/main/VERSIONING.md
- type: VulnerabilityDisclosure
  url: security/cosign-vulnerability-disclosure.yml
- type: Conformance
  url: conformance/cosign-conformance.yml
- type: Sandbox
  url: sandbox/cosign-sandbox.yml
- type: Conventions
  url: conventions/cosign-conventions.yml
- type: ErrorCatalog
  url: errors/cosign-error-codes.yml
- type: Authentication
  url: authentication/cosign-authentication.yml
- type: DataModel
  url: data-model/cosign-data-model.yml
- type: LLMsTxt
  url: llms/cosign-llms.txt
- type: AgentSkill
  url: skills/_index.yml
- type: X-MCPServerCandidate
  url: mcp/cosign-mcp.yml
- type: Plans
  url: plans/cosign-plans-pricing.yml
- type: RateLimits
  url: rate-limits/cosign-rate-limits.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
x-enrichment:
  date: '2026-09-07'
  status: enriched
  artifacts_added: 18
  pass: local-v3
x-parent: sigstore
x-relationship: product

Cosign API — frequently asked questions

Does Cosign have an API?

Yes. APIs.io lists 3 APIs from Cosign, including Cosign CLI, Sigstore Rekor API (consumed) and Sigstore Fulcio API (consumed).

Is there an OpenAPI specification for the Cosign API?

Yes. APIs.io indexes 2 OpenAPI specifications for Cosign, each linked for download from this page.

How do I authenticate with the Cosign API?

Cosign uses bearer-token authentication (6 schemes). The details are profiled on APIs.io as Cosign Authentication.

Is the Cosign API ready for AI agents?

Cosign has a Kin Score of 41.1 out of 100 (developing) and an Agent Readiness score of 21.8 (agent-aware), scored by API Evangelist on 2026-11-06.

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