Compatibility

The Crunch API

crunch-mcp talks to Crunch’s public REST API, version 1, at https://public-api.crunch.co.uk/v1, and logs in through Crunch’s OAuth server at https://oauth.crunch.co.uk. Crunch documents both on its developer site.

	Support
Crunch accounts with public API access	✅ Any account you can log in to and have API access for.
Public OAuth clients (PKCE, no secret)	✅
Confidential OAuth clients (client secret)	✅ The secret is sent with HTTP Basic, alongside PKCE.
Rotating refresh tokens (API applications created since 14 January 2026)	✅ Handled. See Refresh tokens rotate.
Non-rotating refresh tokens (older API applications)	✅ The same refresh token is kept until it expires.
A Crunch sandbox or test environment	❌ Crunch doesn’t offer one. Test with a free Crunch account.

The public API doesn’t cover everything in the Crunch app, and crunch-mcp can only do what the API allows.

Limits of the Crunch API

These come from Crunch’s FAQs and from using the API. They apply whatever crunch-mcp does:

• Rate limit. The API allows about 100 requests per second. crunch-mcp retries automatically when Crunch answers 429 Too Many Requests or 503, waiting as Crunch asks, so you’re unlikely to notice.
• Invoices are in pounds only. The API only creates sales invoices in GBP.
• New invoices only. The API works with Crunch’s new (beta) sales invoices, not the classic invoicing.
• Undocumented endpoints are refused. Calling an endpoint that isn’t part of the public API, such as /banking/statement-entries, returns 403 Forbidden. That’s expected, and it means the data isn’t available through the API.
• Attachments must be data: URIs. Crunch saves anything else as an empty file. crunch-mcp handles this for you. A zero-byte download means the file was uploaded raw by something else.
• 500 errors on creates usually mean bad input. Crunch often returns 500 Internal Server Error when a required field is missing, or a VAT type, expense type or payment method isn’t valid, instead of a clearer error. Check values with the reference tools.
• Closed accounting years can’t be edited, and expenses can only be created in an open period (crunch_list_accounting_periods).
• Reconciled payments can’t be removed, and reconciled expenses can’t be changed or deleted.
• Issued invoices are final. They’re corrected with credit notes in Crunch, not edited or deleted.

Not covered

These parts of Crunch aren’t available through the public API, or aren’t covered by crunch-mcp yet:

• Bank statement entries, bank feeds and reconciliation (only payments recorded against an account are visible)
• VAT returns, Self Assessment, Corporation Tax and other filings
• Payroll, dividends and director’s loan account details beyond what expenses show
• Credit notes, quotes and classic invoices
• Journals, reports and the accounts themselves (profit and loss, balance sheet)

If the public API gains an endpoint for something here, contributions are welcome. The raw tool can reach any public endpoint in the meantime.

Running crunch-mcp

Component	Requirement
Docker image	linux/amd64 or linux/arm64 (for example Raspberry Pi 4/5)
Go (to build without Docker)	1.25 or later
Operating system for the binary	Linux and macOS. Windows should work, but isn’t tested.
Network	Outbound HTTPS to public-api.crunch.co.uk and oauth.crunch.co.uk
MCP clients	Any client supporting Streamable HTTP or stdio. See Connecting MCP clients.

The server is built on the official MCP Go SDK and supports tools, prompts, tool annotations, and image and embedded-resource content in tool results.

Help improve this page

Found an API limit, an error or a gap that isn’t listed here? Open an issue or start a discussion. Please remove any private or financial details first.