LEGION Verify: MCP tool-list history

LEGION Verify — MCP server to detect MCP tool drift (5 read-only tools) · v1.3.0

Did an MCP server change its tools after you approved them? A model reads tool descriptions as instructions, so a silent change to a description or an inputSchema (tool drift, "rug pull") matters. LEGION Verify answers from LEGION's signed, append-only transparency log of MCP tool lists: what a server exposed, and when it changed. Every answer is checked against a keyring anchored on a pinned root key fingerprint (Ed25519, RFC 9162 Merkle proofs); evidence bundles can be re-checked offline.

To pin tool lists in a lockfile and fail CI on drift, see legion-lock.

Tools — all read-only (readOnlyHint: true, destructiveHint: false)

Tool	What it does	Network
get_checkpoint	Latest signed tree head; signature checked against the keyring	GET fixed routes of https://tlog.legion-api.com/tlog/v0
get_server_changes	Signed tool-list history of one MCP server (registry id, limit 1–50), newest first, plus an evidence bundle for the latest record	GET fixed routes of https://tlog.legion-api.com/tlog/v0
verify_evidence_bundle	Verifies a bundle OFFLINE: keyring chain from the pinned root, record signature, signed head, RFC 9162 inclusion proof; optional check against a tools hash you approved (MATCHES_APPROVED / UNAPPROVED_CHANGE)	none
verify_mcp_server	Paste an MCP server URL: matched against the public MCP registry, then the latest signed tool-list record, change count (total / 30 days), RFC 9162 inclusion proof re-checked from the pinned root, and an evidence bundle. live=true adds the tool list served now, compared with the signed one (not signed)	GET https://legion-api.com/drift/verify (default; LEGION_DRIFT_BASE). The live comparison runs only on the hosted endpoint, and only for servers listed in the registry
check_mcp_server	One call for a registry id: signed tool-list fingerprint history, last change with fingerprints before/after and diff link, per-server coverage from the signed COVERAGE_V1 register (full_register is COMPLETE only if observed in every cycle, UNKNOWN if partial), proof URLs, and one command that re-checks everything offline (legion_check kit). Unknown id → UNKNOWN (absence from the log is not a verdict)	GET fixed routes of https://tlog.legion-api.com/tlog/v0 and https://legion-api.com/tlog/v0/coverage

Nothing else: no write, no purchase, no private key, no API key needed. The only caller-supplied URL is the one given to verify_mcp_server: it is looked up in the registry; this server never connects to it. On the hosted endpoint, live=true lets LEGION's drift service send initialize + tools/list to that server, and only if it is a registry entry with a public address.

Connect

Claude Code (remote)

claude mcp add --transport http legion-verify https://mcp.legion-api.com/mcp

Claude Desktop (local, stdio) — claude_desktop_config.json:

{ "mcpServers": { "legion-verify": { "command": "python3", "args": ["/ABSOLUTE/PATH/server.py"] } } }

(requires pip install "mcp==2.1.1"; server.py and legion_tlog_verify.py in the same folder)

Any MCP client (remote): streamable HTTP at https://mcp.legion-api.com/mcp, no auth.

Try it

1. "Call get_checkpoint and give tree_size, root_sha256 and signature_valid."
2. "With get_server_changes, show the signed history of xyz.signomy/civitae (limit 3)."
3. "Pass the evidence_bundle you got to verify_evidence_bundle and tell me whether the proof is valid."
4. "Use verify_mcp_server on https://tandem.ac/mcp with live=true: did its tools change since the signed record?"

Same check in a browser, with an embeddable badge: https://legion-api.com/drift/check/

Verify the whole log yourself (no MCP, no pip)

PIN=a7c6a35b1c2c81d589a30c2ad628679bdea9da4139d49aa3c42cdde6e1c65036
curl -fsSLO https://legion33shadow.github.io/legion-tlog-mirror/legion_verify_mirror.py
python3 -I -S legion_verify_mirror.py "$PIN"

Root key fingerprint — pin it out of band: a7c6a35b1c2c81d589a30c2ad628679bdea9da4139d49aa3c42cdde6e1c65036

Limits

The log is the signed record of one observer (LEGION); it does not show what a server serves to other clients. Only name, description and inputSchema are fingerprinted. A change appears only after the next LEGION observation and the next signed head. Bitcoin anchors are pending (no ots verify on a full node yet). No independent witness has cosigned yet. Servers that require auth are not observed.

Public server (v1.3.0): immutable proofs and per-head history are cached; each client (IP seen by Cloudflare) may trigger at most 20 uncached log requests per minute (CLIENT_RATE_LIMITED otherwise; cached answers still served).

License: MIT (see LICENSE).