satsignal-mcp 0.2.1

MCP server exposing Satsignal tamper-evident anchoring as agent-callable tools.

satsignal-mcp

MCP server exposing Satsignal tamper-evident anchoring as agent-callable tools.

Any MCP-compatible client (Claude Desktop, Claude Code, agent frameworks that speak MCP over stdio) can call Satsignal directly — no custom SDK required.

What it does

Each anchor call computes a sha256 of the input client-side and sends only the hash to proof.satsignal.cloud. The file/text/JSON bytes never leave the calling machine. The server records the hash on the BSV blockchain and returns a receipt the agent can save or pass on.

Tools

Tool	Auth	What it does
anchor_file	yes	sha256 a local file, anchor the digest
anchor_text	yes	sha256 a UTF-8 string, anchor the digest
anchor_json	yes	canonicalize JSON (sorted keys, compact, UTF-8), sha256, anchor
lookup_hash	no	check if a sha256 is on-chain
verify_bundle	no	open a local .mbnt and chain-confirm via lookup_hash

anchor_* tools accept dry_run: true to preview the sha256 without broadcasting. The Satsignal API itself does not honor dry_run — the flag lives in this MCP layer and short-circuits before any network call.

Folder selection

Each anchor_* tool accepts a folder property naming the workspace folder the receipt lands in (defaults to SATSIGNAL_FOLDER, then the legacy SATSIGNAL_MATTER, then inbox).

Legacy compat: the old input name matter is a frozen alias of folder — still accepted with byte-identical behavior and never removed. Sending both folder and matter with different non-empty values is rejected (conflicting_alias); equal values are accepted. The request sent to the Satsignal API still uses the frozen matter_slug wire field, so this MCP server keeps working against current and older / self-hosted Satsignal servers.

Configuration

Env var	Required	Default
SATSIGNAL_API_KEY	for anchoring	—
SATSIGNAL_API_BASE	no	https://app.satsignal.cloud
SATSIGNAL_FOLDER	no	inbox
SATSIGNAL_MATTER	no	legacy alias of SATSIGNAL_FOLDER (still honored; SATSIGNAL_FOLDER wins if both set)

Get an API key at https://app.satsignal.cloud. The customer API (POST /api/v1/anchors, bundle download, dashboard) lives on app.satsignal.cloud. proof.satsignal.cloud is the public verifier surface and serves /lookup_hash in mirror-mode — verify_bundle works against either host, but anchoring requires app.*. v0.1.0 shipped with the wrong default and silently 404'd every anchor call.

Install

pip install satsignal-mcp

Claude Desktop config

Add this to claude_desktop_config.json:

{
  "mcpServers": {
    "satsignal": {
      "command": "satsignal-mcp",
      "env": {
        "SATSIGNAL_API_KEY": "sk_...",
        "SATSIGNAL_FOLDER": "case-123"
      }
    }
  }
}

Verification model

Each anchor returns a proof_id, txid, and proof_url (carrying the legacy bundle_id / receipt_url values, which are still present). The proof is independent of Satsignal: anyone can fetch the bundle, verify the on-chain transaction directly against BSV, and check the sha256 matches. satsignal-cli performs the full cryptographic + chain verification; verify_bundle in this MCP server does a faster chain-confirm only (matches the bundle's claimed txid against what the public /lookup_hash index reports for that sha).

Security notes

• The label, filename, and folder (sent on the wire as the frozen matter_slug) fields you pass are written into the receipt and rendered on the public verifier page. They are also attacker-controllable from any agent calling this server — downstream code that reads these fields should treat them as untrusted text (HTML-escape, never embed in LLM context without an isolation boundary).
• The API key is sent as Authorization: Bearer … over HTTPS and is never logged or returned in tool output.

License

MIT.