PowerSync DevTools MCP Tools

PowerSync DevTools exposes MCP (Model Context Protocol) tools that let a coding agent, such as Claude Code or Codex, query your app’s local database, read its sync status, and run sync actions.

These tools work with your running app. To let an agent search the PowerSync documentation, use the docs MCP server instead.

Endpoints

Host	Endpoint
Vite	`http://localhost:5173/__devtools/__mcp` (use your dev server port)
Nuxt DevTools 4	`http://localhost:3000/__devtools/__mcp` (use your dev server port)
Node.js	`<url>/__mcp`, where `url` is the value that `enablePowerSyncDiagnostics()` returns

Nuxt DevTools 3 does not have an MCP endpoint. On the web, the tools get the database from an open app tab. Keep your app open in a browser that Vite DevTools trusts, or the tools return an error. For a Node.js app, set a fixed port in enablePowerSyncDiagnostics() so that the endpoint stays the same when your app restarts.

Connect a Coding Agent

The endpoint accepts only requests that have a loopback Origin header, such as http://localhost:5173. Some MCP clients do not send this header, so add it to the client configuration. For example, to add the Vite endpoint to Claude Code:

claude mcp add --transport http powersync-devtools http://localhost:5173/__devtools/__mcp --header "Origin: http://localhost:5173"

If your MCP client cannot send the header, set allowedOrigins: false. Read Origin and Authorization.

Coding agents such as Claude Code can add the server themselves. Start your dev server, open your app, and give the agent a prompt like this one:

Connect to the PowerSync DevTools MCP server of my running app.
The endpoint is http://localhost:5173/__devtools/__mcp. It uses the Streamable HTTP transport.
Every request must send the header "Origin: http://localhost:5173".
Add the server, then call powersync_sources and powersync_status and tell me the sync state.

Change the URL and the port to match your host. Some agents must restart before they can use a new MCP server.

Tools

The tools take positional arguments named arg0 and arg1. The last argument of most tools is the database ID. Pass null to use the first attached database, or call powersync_sources to list the IDs.

Tool	Arguments	Returns
`powersync_sources`	None	The attached databases, with their ID and SDK.
`powersync_query`	`arg0`: `{ sql, params? }` `arg1`: database ID or `null`	`{ columns, rows }`. Each row is an array in column order.
`powersync_schema`	`arg0`: database ID or `null`	The schema, as the PowerSync SQLite core receives it.
`powersync_info`	`arg0`: database ID or `null`	The endpoint, the token, the client ID, the connection method, and the core version.
`powersync_status`	`arg0`: database ID or `null`	The last sync status that the client reported.
`powersync_upload-queue`	`arg0`: database ID or `null`	The number and size of the local changes that wait to upload.
`powersync_action`	`arg0`: `{ action, args? }` `arg1`: database ID or `null`	Runs one of these actions: `reconnect`, `disconnect`, `clearData`, `requestCheckpoint`, `subscribeStream`, `unsubscribeStream`.

For subscribeStream and unsubscribeStream, args is { name, params?, ttl?, priority? }.

powersync_query can change data. powersync_action with clearData deletes the local data, including the local changes in the upload queue, and downloads the data again. powersync_info returns the current JWT. Give these tools only to agents that you trust.

Origin and Authorization

To change how the endpoint checks requests, use the mcp setting:

Value	Result
`'auto'`	The default. The endpoint accepts requests with a loopback `Origin` header.
`{ allowedOrigins: false }`	The endpoint also accepts requests without an `Origin` header. Use this only when the server listens on `localhost`.
`{ authorization: '<token>' }`	Requests must also send `Authorization: Bearer <token>`. Read the token from an environment variable.
`false`	Turns off the endpoint.

Set it in your host:

Vite 8
Vite 7
Nuxt DevTools 4
Node.js

export default defineConfig({
  devtools: { apply: 'serve', mcp: { allowedOrigins: false } },
  plugins: [powersyncDevtools()]
});

export default defineConfig({
  plugins: [...(await DevTools({ mcp: { allowedOrigins: false } })), powersyncDevtools()]
});

export default defineNuxtConfig({
  vite: {
    devtools: { mcp: { allowedOrigins: false } }
  }
});

const devtools = await enablePowerSyncDiagnostics(db, { mcp: { allowedOrigins: false } });

Test the Endpoint

Use curl to check that the endpoint works. This example counts the operations in the local oplog:

curl -X POST http://localhost:5173/__devtools/__mcp \
  -H 'Origin: http://localhost:5173' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"powersync_query","arguments":{"arg0":{"sql":"SELECT count(*) AS operations FROM ps_oplog"},"arg1":null}}}'

If the response is 403 Forbidden, the request has no loopback Origin header.

Get Started

Configuration Details

Sync Streams

Client SDKs

Handling Writes

Maintenance & Ops

Integrations

Tools

Resources

PowerSync DevTools MCP Tools

Endpoints

Connect a Coding Agent

Tools

Origin and Authorization

Test the Endpoint

​Endpoints

​Connect a Coding Agent

​Tools

​Origin and Authorization

​Test the Endpoint

Endpoints

Connect a Coding Agent

Tools

Origin and Authorization

Test the Endpoint