MCP

The whole Secondlayer surface as Model Context Protocol tools, 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):

{
  "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).

An HTTP transport (@secondlayer/mcp-http) adds 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; see Authentication	—
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

Start here

Read these resources before calling tools:

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 six domains. Reads are cursor-paginated; writes that kick off work (reindex, backfill, replay, deploy) return an operationId to 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.
See the REST API for the underlying endpoints.