mcp

Verifiable provenance for AI agents — ZK proofs over confidential documents, no plaintext exposure.

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What it can do

    What data it sees

    Do you need an account

    An API key from the service settings is required

    Verifiable provenance for AI agents — ZK proofs over confidential documents, no plaintext exposure.

    How to connect

    How to connect mcp to Claude

    The server address to paste into Claude settings:

    https://mcp.lemma.workers.dev/mcp

    1. Open Claude (claude.ai or the desktop app).
    2. Go to Settings → Connectors.
    3. Click Add custom connector.
    4. Paste the server address copied below into Remote MCP server URL and click Add.
    5. In a chat, click + → Connectors and switch the new connector on.

    Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

    Authorization

    After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

    How to connect mcp to ChatGPT

    The server address to paste into ChatGPT settings:

    https://mcp.lemma.workers.dev/mcp

    1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
    2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
    3. Open Settings → Connectors and click Create.
    4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
    5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
    6. In a new chat open + → Apps/Connectors and enable the connector.

    OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

    Authorization

    On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

    How to connect mcp to Cursor

    The server address to paste into Cursor settings:

    https://mcp.lemma.workers.dev/mcp

    Fastest: click Open in Cursor below and confirm the prompt.

    Manually:

    1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
    2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
    3. Save the file. The server appears in the MCP list; authorize it there if asked.

    Authorization

    If the service needs sign-in, an authorize button appears next to the server in the MCP list.

    Server tool list (5)

    Raw names from tools/list. Only developers need these.

    lemma_query_verified_attributesQuery cryptographically verified attributes from Lemma. Use this as the primary tool for finding documents whose attributes match given conditions (e.g., "subject's birthYear lt 2008"). Returns { results: Array<{ docHash, schema, issuerId, subjectId, attributes, isVerified, proof?: { status, circuitId, chainId }, disclosure? }>, hasMore }. The MCP layer enriches each item with an `isVerified` flag derived from `proof.status` (true when status is 'verified' or 'onchain-verified'). Use lemma_get_proof_status to monitor a specific proof; use lemma_get_schema to interpret the keys returned in `attributes`.
    lemma_get_schemaRetrieve a Lemma schema by its ID via GET /v1/schemas/{id}. A schema declares how documents of a given type are interpreted and normalized. Returns SchemaMeta { id, description? } with additionalProperties open — implementations commonly include a `normalize` artifact (WASM that maps raw documents to canonical form) and its content hash. Use this when you need to interpret attribute keys returned by lemma_query_verified_attributes.
    lemma_get_circuitRetrieve a zero-knowledge proof circuit by its circuitId via GET /v1/circuits/{circuitId}. A circuit defines the constraints that proofs must satisfy and binds to a single schema. Returns CircuitMeta { circuitId, schema, description?, inputs?, verifier?: { type: 'onchain'|'offchain', address?, chainId? }, artifact?: { location: { type: 'ipfs'|'https', wasm, zkey } } }. Use this before lemma_submit_proof to confirm the circuit's schema, public inputs, and verifier configuration. Circuits are immutable; new variants get new circuitIds.
    lemma_get_generatorRetrieve a Lemma document generator by generatorId via GET /v1/doc-generators/{generatorId}. A generator describes how a class of source documents is produced (e.g., what fields a 'KYC-v2' issuer must populate). Returns GeneratorMeta { generatorId, schema, description?, language?, source?: { type: 'url', uri }, inputsSpec?, outputsSpec? }. Each generator is bound to one schema. Use this when onboarding a new issuer or auditing how an existing schema is being populated.
    lemma_get_proof_statusGet the verification status of a proof. NOTE: the v2 API does not yet expose a dedicated GET /v1/proofs/{id} endpoint, so this tool internally calls POST /v1/verified-attributes/query filtered by docHash (treating the verificationId returned from lemma_submit_proof as a docHash filter). Returns { status, circuitId, chainId, docHash } extracted from the matched item, or undefined if the verificationId is unknown. Status enum: received | verified | onchain-verified | rejected. Use the SDK's isVerified() helper (or check status === 'verified' || status === 'onchain-verified') to determine cryptographic validity.