Build

For developers and agents

Everything the swap form knows can be read by a machine: the catalogue, limits, live quotes, address checks and swap status. No account, no key. An agent that controls a wallet can also create a swap and pay the instruction it gets back.

The files and endpoints

Address	Format	What it is for
https://api.sablebolt.io/mcp	MCP, Streamable HTTP	Eight tools: seven read-only and create_swap
/openapi.json	OpenAPI 3.1	The REST API at api.sablebolt.io: assets, routes, limits, quotes, address check, swaps, webhooks, market data
/.well-known/agent-skills/index.json	JSON	Eight skills, each mapped to endpoints and a documentation page
/.well-known/agent-card.json	JSON	The A2A agent card: interfaces, skills with example questions, the hand-off rule
/llms.txt	Markdown	The index for assistants; every page has a markdown twin at its own path plus .md
/feed.xml	RSS 2.0	The blog, one item per post

The MCP endpoint

https://api.sablebolt.io/mcp

Transport: Streamable HTTP, protocol version 2025-06-18, stateless: no session to open, no stream to keep. GET answers 405, DELETE 405.
Authentication: none. Rate: 60 requests a minute per IP on the endpoint; swap creation 10 a minute per IP, shared with the REST route.
One JSON-RPC request per HTTP call. A batch is refused with 400.
Every tool carries a title and annotations: readOnlyHint on the seven read tools; create_swap is marked as not read-only and not destructive.

Tool	Input	Returns	Kind
`list_assets`	—	every asset the form knows: slug, ticker, network, confirmations, extra-id name, availability	read-only
`list_routes`	—	every route with its own page, and whether both sides are available right now	read-only
`get_limits`	from, to	minimum and maximum for the route, in the asset you send	read-only
`get_quote`	from, to, amount	amountTo, networkFee (taken out of the payout), receiveAmount, rate; the final amount is set when the deposit confirms	read-only
`validate_address`	asset, address	whether the address has the right format for the asset; not who owns it, not whether an exchange needs a memo	read-only
`get_swap_status`	id	stage (1 waiting … 5 done), both addresses, amounts, both transaction hashes; the payment instruction while the deposit is awaited	read-only
`swap_page_link`	from, to, amount (optional)	the page where a person completes the swap, with the amount prefilled	read-only
`create_swap`	from, to, amount, fromAddress, toAddress; extraId and fromExtraId when a chain needs them	the swap id, the status page and the payment instruction	creates a swap

Connect a client

Claude Code

One command adds the endpoint as an HTTP server:

claude mcp add --transport http sablebolt https://api.sablebolt.io/mcp

Claude.ai and Claude Desktop

Settings → Connectors → Add custom connector, then paste the endpoint URL. There is no sign-in step: the server asks for no credentials.

Cursor

In .cursor/mcp.json in the project, or ~/.cursor/mcp.json for every project:

{
  "mcpServers": {
    "sablebolt": { "url": "https://api.sablebolt.io/mcp" }
  }
}

ChatGPT

Settings → Connectors → Developer mode → Create, then name the connector and paste the endpoint URL.

Any other client

A Streamable HTTP client that sends initialize, then tools/list and tools/call, works as is. Send Accept: application/json, text/event-stream; the answer comes back as JSON or as one SSE message.

The hand-off rule

A swap for a person is completed by that person on the page: the assistant hands over swap_page_link, the person checks the amount, both addresses and the memo on screen, then sends the deposit from their own wallet.

create_swap is for an agent that controls the sending wallet itself. The sender address is required on every swap. The form has no refund address: a swap that cannot be completed is handled by support.

The rate floats until the deposit confirms. A quote is an estimate; the payout is set at confirmation.

The payment instruction

create_swap (and POST /v1/swaps) returns a payment instruction next to the deposit address, so an agent with a wallet pays without guessing:

Field	Meaning
`asset, chain, chainId`	the asset slug, the chain it moves on and, on EVM chains, the numeric chain id (1 Ethereum, 56 BNB Smart Chain, 137 Polygon, 8453 Base); null elsewhere
`tokenContract, decimals`	the token contract or mint and the precision as the liquidity partner lists them; no contract for a chain's own coin
`address, extraId, extraIdName`	the one-time deposit address and, when the chain needs one, the memo or destination tag under its own name; without it the deposit is not matched
`amount, amountBaseUnits`	the exact amount to send, in the asset and in base units (satoshi, wei, sun); the base-unit value is rounded up at the last unit, never down
`uri, uriStandard`	a wallet URI where a standard exists: BIP-21 for Bitcoin-like coins, ERC-681 for EVM coins and tokens, Solana Pay, monero:, ton://transfer; null where none applies
`note`	the one rule in words: send exactly this amount in one transaction from the sending address given
`statusUrl (on the swap)`	the status page; get_swap_status and GET /v1/swaps/{id} return the same stages

The REST API

Described in /openapi.json. Every answer is JSON under data, every error under error with a code. 200 requests a minute per IP across the API, with tighter caps per route:

Endpoint	What it returns
`GET /v1/assets`	every asset, with canSend and canReceive
`GET /v1/routes`	every published route
`GET /v1/limits?from=&to=`	min and max for the route; 60 a minute
`GET /v1/quote?from=&to=&amount=`	the estimate, also as POST with a JSON body; 60 a minute
`POST /v1/address/validate`	the address format check; 30 a minute
`POST /v1/swaps`	creates a swap and returns the payment instruction; 10 a minute, shared with create_swap
`GET /v1/swaps/{id}`	status, stage, both addresses, both transaction hashes; 60 a minute
`POST /v1/swaps/{id}/notify`	registers an https URL and a secret for signed swap.status notifications (HMAC-SHA256 over timestamp and body); DELETE removes it; 10 a minute
`GET /v1/network/{chain}, /v1/market/prices, /v1/market/chart/{id}`	chain statistics and market data for the pages, cached

Changelog

2026-11-03: This page. Listed in the official MCP Registry (registry.modelcontextprotocol.io) as io.sablebolt/swaps.
2026-11-02: create_swap and the payment instruction (base units, token contract, decimals, wallet URI); signed swap.status webhooks; canSend and canReceive on every asset; the A2A agent card; payment links at /pay; JSON-RPC batches refused; one creation cap for REST and MCP.
2026-10-28: Launch: REST API v1 described in OpenAPI 3.1, the MCP endpoint with the read tools, llms.txt and markdown twins, the agent-skills index, RSS.

Contact

Questions and bug reports: support@sablebolt.io, or @sablebolt_bot on Telegram. Security reports: the address in /.well-known/security.txt.