You Need A Budget (YNAB) MCP

Instructions

Implementation Reference

• src/ynab_mcp_server/server.py:180-197 (handler)

  The main handler for executing the 'list-accounts' tool. Validates input using ListAccountsInput, determines budget_id, fetches accounts via ynab_client, formats and returns the list.

  elif name == "list-accounts":
      args = ListAccountsInput.model_validate(arguments or {})
      budget_id = await _get_budget_id(args.model_dump())
      accounts = await ynab_client.get_accounts(budget_id=budget_id)
  
      if not accounts:
          return [types.TextContent(type="text", text="No accounts found for this budget.")]
  
      account_list = "\n".join(
          f"- {acc.name} (ID: {acc.id}): {acc.balance / 1000:.2f} (Type: {acc.type})"
          for acc in accounts
      )
      return [
          types.TextContent(
              type="text",
              text=f"Here are the accounts for budget {budget_id}:\n{account_list}",
          )
      ]

• src/ynab_mcp_server/tool_models.py:93-94 (schema)

  Pydantic model for the input schema of 'list-accounts' tool. Inherits from BudgetIdInput, allowing optional budget_id.

  class ListAccountsInput(BudgetIdInput):
      pass

• src/ynab_mcp_server/tool_models.py:7-11 (schema)

  Base Pydantic model providing the optional budget_id field used by ListAccountsInput schema.

  class BudgetIdInput(BaseModel):
      budget_id: Optional[str] = Field(
          None,
          description="The ID of the budget. If not provided, the default budget will be used.",
      )

• src/ynab_mcp_server/server.py:54-58 (registration)

  Registration of the 'list-accounts' tool in the list_tools handler, including name, description, and schema reference.

  types.Tool(
      name="list-accounts",
      description="List all accounts for a given budget. Useful for getting account IDs for other tools.",
      inputSchema=ListAccountsInput.model_json_schema(),
  ),

• src/ynab_mcp_server/server.py:142-152 (helper)

  Helper function used by list-accounts handler to resolve the budget_id from input arguments, settings, or default budget.

  async def _get_budget_id(arguments: dict | None) -> str:
      """Gets the budget_id from arguments, settings, or falls back to the default budget."""
      if settings.ynab_default_budget_id:
          return settings.ynab_default_budget_id
  
      if arguments and "budget_id" in arguments and arguments["budget_id"]:
          return arguments["budget_id"]
  
      budget = await ynab_client.get_default_budget()
      return budget.id