MCP

The whole Secondlayer surface as Model Context Protocol tools. Point an agent at the server and it can query decoded chain data, deploy and manage subgraphs, wire up webhooks, and discover contracts — over one connection, with the same auth as the SDK and CLI.

Connect

The server ships as @secondlayer/mcp and speaks stdio. Add it to any MCP client (Claude Code, Cursor, Claude Desktop, or any MCP host):

{
  "mcpServers": {
    "secondlayer": {
      "command": "npx",
      "args": ["-y", "@secondlayer/mcp"],
      "env": { "SL_API_KEY": "sk-sl_..." }
    }
  }
}

SL_API_KEY is optional — leave it out for anonymous reads (see Authentication).

There's also an HTTP transport (@secondlayer/mcp-http) with session management and optional SECONDLAYER_MCP_SECRET bearer auth, for hosting the server behind a URL.

Pay-per-call (x402)

For accountless usage, set a Stacks key and the server auto-pays HTTP 402 challenges per call:

X402_PRIVATE_KEY=...          # signs x402 payments
X402_TOPUP_USD=5.00           # optional: auto top-up the prepaid balance
X402_TOPUP_WHEN_BELOW=$0.50   # optional: top-up threshold

Authentication

Surface	Reads	Writes
Index	Anonymous, or any key incl. free-tier (free reads cover the recent 24h window; older history is pay-as-you-go credits or a plan)	—
Contracts, Scaffold	Public, no key	—
Subgraphs	Public subgraphs keyless; private need your key	Need your key
Streams, Subscriptions, Account	Need your key	Need your key

An agent holding an account-level key can mint its own scoped read keys with account_create_key. Keys and signing secrets are returned once — capture and forward them to the user.

Start here

The server exposes MCP resources for orientation — read these before calling tools so the agent knows what exists and what filters are valid:

Resource	What it returns
`secondlayer://context`	Live snapshot — your subgraphs, subscriptions, account, chain tips, auth state, and what you can do. Read first.
`secondlayer://filters`	Event filter types and the fields each accepts
`secondlayer://column-types`	Subgraph column types, SQL mappings, and options
`secondlayer://traits`	SIP standards you can classify and scaffold against (sip-009/010/013)
`secondlayer://chain-triggers`	Chain-subscription trigger types and their filter fields

For Index specifically, call index_discover to learn every event type, its columns, and the filters it accepts before building queries.

Tools

Thirty-three tools across seven domains. Reads are cursor-paginated; writes that kick off work (reindex, backfill, replay, deploy) return an operationId you can poll.

Index — decoded reads

Tool	What it does
`index_events`	Decoded events by `eventType` (stx/ft/nft mint·burn, print, …), with `trait` scoping
`index_ft_transfers`	Decoded SIP-010 fungible-token transfers
`index_nft_transfers`	Decoded SIP-009 non-fungible-token transfers
`index_contract_calls`	Decoded contract calls — function, args, result
`index_transactions`	Decoded transactions, filterable by type/sender/contract
`index_blocks`	Decoded blocks
`index_discover`	The Index vocabulary: event types, columns, allowed filters
`index_print_schema`	Per-topic print payload schemas for a contract, inferred from on-chain history — read before writing `print_event` handlers
`batch_query`	Up to 10 public `/v1` reads in one round trip

Subgraphs — your own indexer

Tool	What it does
`subgraphs_deploy`	Deploy from `defineSubgraph()` source (managed or BYO Postgres; `dryRun` previews DDL)
`subgraphs_list`	List your deployed subgraphs
`subgraphs_get`	Full detail — schema, health, table columns
`subgraphs_query`	Query a table with operator filters (`amount.gte`, `name.like`, …)
`subgraphs_gaps`	List missing block ranges
`subgraphs_backfill`	Non-destructive forward fill of a block range
`subgraphs_reindex`	Drop + reprocess a block range
`subgraphs_stop`	Cancel an in-flight reindex/backfill
`subgraphs_publish`	Claim the global public name; anon-readable at `/v1/subgraphs/<name>`
`subgraphs_unpublish`	Make it private again
`subgraphs_delete`	Delete a subgraph and its data

Streams — raw firehose

Tool	What it does
`streams_dumps`	List the signed bulk dumps manifest (cold backfill). Live Streams reads are REST-only at `/v1/streams/*`.

Subscriptions — webhooks

Tool	What it does
`subscriptions_create`	Create a subgraph- or chain-triggered webhook (returns `signingSecret` once)
`subscriptions_list`	List subscriptions
`subscriptions_get`	Full detail — filter, auth, retry, circuit state
`subscriptions_update`	Patch url, filter, auth, retry, timeout, concurrency
`subscriptions_test`	Send a one-off SSRF-guarded test delivery
`subscriptions_replay`	Replay a block range
`subscriptions_delete`	Delete a subscription

Contracts & scaffold

Tool	What it does
`contracts_find`	Discover deployed contracts conforming to a trait (sip-010/009/013)
`get_contract_abi`	Fetch a deployed contract's full ABI from the registry
`scaffold_from_contract`	Generate a subgraph scaffold from a contract's ABI

Account

Tool	What it does
`account_whoami`	The authenticated account's email and plan
`account_create_key`	Mint a scoped streams/index read key (returned once)

Notes

One-time secrets. account_create_key and subscriptions_create return a key/secret exactly once — forward it to the user.
Cursors are opaque and per-keyspace: contract-call cursors are not interchangeable with event cursors.
Tail without streaming. For subgraph tables, sort _id desc for the latest, then poll forward with {"_id.gt": "<last id>"}, order asc.
Every surface shares one session — sign in once and the SDK, CLI, and MCP server all inherit it. See the REST API for the underlying endpoints.