Build an agent

Install the SDKCopy Anchor Link

npm install @modelcontextprotocol/sdk

Connect and call a public toolCopy Anchor Link

No account needed for identity, stores and market data.

import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';

const client = new Client({ name: 'my-agent', version: '1.0.0' });
await client.connect(
  new StreamableHTTPClientTransport(new URL('https://mcp.swopme.co/mcp')),
);

const { tools } = await client.listTools();
console.log(`${tools.length} tools`); // 51

const result = await client.callTool({
  name: 'swop_lookup_identity',
  arguments: { handle: 'travis.swop.id' },
});
console.log(JSON.parse(result.content[0].text).data.evmAddress);

await client.close();

Every tool returns one text item holding JSON. On failure the result has isError: true and the text explains why.

Let your model choose toolsCopy Anchor Link

Pass the tools list (each has name, description and a JSON Schema inputSchema) to your model as function definitions, and route the model's tool calls back through callTool. The descriptions are written for models: they say when to use each tool, which tool to call next, and when to ask the user first.

Also pass along the server's instructions (returned from initialize; client.getInstructions() in TypeScript). They tell the model what Swop can do for this endpoint and how to behave, including always confirming prices and payments with the user.

Sign in for account toolsCopy Anchor Link

Calling an account tool without a token fails with HTTP 401 and JSON-RPC error -32001 ("Not linked to a Swop account"). The fix is OAuth: the SDKs can run the whole flow if you give them an auth provider.

const transport = new StreamableHTTPClientTransport(
  new URL('https://mcp.swopme.co/mcp'),
  { authProvider: myOAuthProvider },
);

new StreamableHTTPClientTransport(new URL('https://mcp.swopme.co/mcp'), {
  requestInit: { headers: { Authorization: `Bearer ${accessToken}` } },
});

The endpoints, token lifetimes and scopes are in Account linking & caps.

Handle money tools in two callsCopy Anchor Link

Money and posting tools return a preview first. Show it to your user, and only after they approve call again with previewId and confirm: true:

const preview = await client.callTool({
  name: 'swop_send',
  arguments: { to: 'maya.swop.id', amountUsd: 25 },
});
const { previewId, summary } = JSON.parse(preview.content[0].text);
// e.g. summary: "Send 25 USDC (~$25.00) on base to maya.swop.id (Maya)"
// Show it (and the caps in the preview) to the user. Only on their explicit yes:
await client.callTool({
  name: 'swop_send',
  arguments: { to: 'maya.swop.id', amountUsd: 25, previewId, confirm: true },
});

For swop_send, the confirm call must restate the same recipient, token, chain and amount. The exact preview fields for each tool are in the tool reference.