specification: API Commons MCPServer
specificationVersion: '0.1'
provider: Cosign
providerId: cosign
generated: '2026-09-07'
method: derived
status: candidate
source: >-
  Derived from the published Cosign CLI reference at
  https://github.com/sigstore/cosign/tree/main/doc . Searched for a first-party server on
  2026-09-07 (web search plus the sigstore GitHub organization); none exists.
description: >-
  NO OFFICIAL MCP SERVER EXISTS for Cosign or for any Sigstore project as of 2026-09-07. Neither a
  hosted endpoint nor a published stdio package was found. The tool list below is a CANDIDATE derived
  from Cosign's own documented CLI commands so the shape of a future server is recorded; it is not
  something an agent can call today, and no MCPServer pointer is emitted for it.
deployment:
  mode: none
  endpoint: null
  install: null
  package: null
  auth: unknown
  verified: searched
search_evidence:
  - what: Web search for an official Sigstore/Cosign MCP server
    date: '2026-09-07'
    result: >-
      No first-party server found. Results discuss using cosign to SIGN MCP servers and their
      container images — the inverse relationship — not a Cosign MCP server.
  - what: sigstore GitHub organization
    url: https://github.com/sigstore
    date: '2026-09-07'
    result: No mcp-server repository.
  - what: /.well-known/ probes across all five Sigstore hosts
    file: well-known/cosign-well-known.yml
    date: '2026-09-07'
    result: No ai-plugin.json, no agent card, nothing naming an MCP endpoint.
candidate_tools:
  - name: cosign_verify
    description: Verify a signature on a container image against an identity or key.
    backing_command: cosign verify
    consequence: read-only
  - name: cosign_verify_blob
    description: Verify a signature on a blob.
    backing_command: cosign verify-blob
    consequence: read-only
  - name: cosign_verify_attestation
    description: Verify an in-toto attestation on a container image.
    backing_command: cosign verify-attestation
    consequence: read-only
  - name: cosign_tree
    description: List signatures, SBOMs and attestations attached to an image.
    backing_command: cosign tree
    consequence: read-only
  - name: cosign_download_sbom
    description: Download an SBOM attached to an image.
    backing_command: cosign download sbom
    consequence: read-only
  - name: cosign_download_attestation
    description: Download an attestation attached to an image.
    backing_command: cosign download attestation
    consequence: read-only
  - name: cosign_sign
    description: Sign a container image.
    backing_command: cosign sign
    consequence: irreversible-side-effect
    warning: >-
      Keyless signing writes a permanent, public entry to the Rekor transparency log, including the
      signer identity. It cannot be undone. See conventions/cosign-conventions.yml reversibility.
  - name: cosign_attest
    description: Create and attach an attestation to a container image.
    backing_command: cosign attest
    consequence: irreversible-side-effect
  - name: cosign_clean
    description: Remove attached signatures/attestations from an image in a registry.
    backing_command: cosign clean
    consequence: destructive-but-reversal-only
    note: Reverses the registry-side effect of sign/attest; does NOT remove the transparency-log entry.
note: >-
  Wired into apis.yml as X-MCPServerCandidate, NOT as MCPServer, because no server exists to point
  at. Promote it only if Sigstore publishes one.